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Although a member of the Triple Alliance, Italy did not join the Central Powers – Germany and Austria-Hungary – when the war started with Austria-Hungary's declaration of war on Serbia on 28 July 1914. In fact, the two Central Powers had taken the offensive while the Triple Alliance was supposed to be a defensive alliance. Moreover the Triple Alliance recognized that both Italy and Austria-Hungary were interested in the Balkans and required both to consult each other before changing the status quo and to provide compensation for whatever advantage in that area: Austria-Hungary did consult Germany but not Italy before issuing the ultimatum to Serbia, and refused any compensation before the end of the war.

Almost a year after the war's commencement, after secret parallel negotiations with both sides (with the Allies in which Italy negotiated for territory if victorious, and with the Central Powers to gain territory if neutral) Italy entered the war on the side of the Allied Powers. Italy began to fight against Austria-Hungary along the northern border, including high up in the now-Italian Alps with very cold winters and along the Isonzo river. The Italian army repeatedly attacked and, despite winning a number of battles, suffered heavy losses and made little progress as the terrain favoured the defender. In 1916, the Italians stopped the Südtirol Offensive and conquered Gorizia. However, Italy was then forced to retreat in 1917 by a German-Austrian counteroffensive at the Battle of Caporetto after Russia left the war, allowing the Central Powers to move reinforcements to the Italian Front from the Eastern Front.

The offensive of the Central Powers was stopped by Italy at the Battle of Monte Grappa in November 1917 and the Battle of the Piave River in May 1918. Italy took part in the Second Battle of the Marne and the subsequent Hundred Days Offensive in the Western Front. On 24 October 1918 the Italians, despite being outnumbered, breached the Austrian line in Vittorio Veneto; as a result, the centuries-old Habsburg Empire collapsed. Italy recovered the territory lost after the fighting at Caporetto in November the previous year and moved into Trento and Trieste. Fighting ended on 4 November 1918. Italian armed forces were also involved in the African theatre, the Balkan theatre, the Middle Eastern theatre and then took part in the Occupation of Constantinople. At the end of World War I, Italy was recognized with a permanent seat in the League of Nations' executive council along with Britain, France and Japan.

Roy Pryce summarized the experience as follows:

The government's hope was that the war would be the culmination of Italy's struggle for national independence. Her new allies promised her the "natural frontiers" which she had so long sought-the Trentino and Trieste-and something more. At the end of hostilities she did indeed extend her territory, but she came away from the peace conference dissatisfied with her reward for three and a half years' bitter warfare, having lost half a million of her noblest youth, with her economy impoverished and internal divisions more bitter than ever. That strife could not be resolved within the framework of the old parliamentary regime. The war that was to have been the climax of the Risorgimento produced the Fascist dictatorship. Something, somewhere, had gone wrong.^[1]

Italy was a member of the Triple Alliance with Germany and Austria-Hungary. Despite this, in the years before the war, Italy had enhanced its diplomatic relationships with the United Kingdom and France. This was because the Italian government had grown convinced that support of Austria (the traditional enemy of Italy during the 19th century Risorgimento) would not gain Italy the territories it wanted: Trieste, Istria, Zara and Dalmatia, all Austrian possessions. In fact, a secret agreement signed with France in 1902 sharply conflicted with Italy's membership in the Triple Alliance.

A few days after the outbreak of the war, on 3 August 1914, the government, led by the conservative Antonio Salandra, declared that Italy would not commit its troops, maintaining that the Triple Alliance had only a defensive stance and Austria-Hungary had been the aggressor. Thereafter Salandra and the minister of Foreign Affairs, Sidney Sonnino, began to probe which side would grant the best reward for Italy's entrance in the war or its neutrality. Although the majority of the cabinet (including former Prime Minister Giovanni Giolitti) was firmly against intervention, numerous intellectuals, including Socialists such as Ivanoe Bonomi, Leonida Bissolati, and, after 18 October 1914, Benito Mussolini, declared in favour of intervention, which was then mostly supported by the Nationalist and the Liberal parties. Pro-interventionist socialists believed that, once that weapons had been distributed to the people, they could have transformed the war into a revolution.

The negotiation with Central Powers to keep Italy neutral failed: after victory Italy was to get Trentino but not the South Tyrol, part of the Austrian Littoral but not Trieste, maybe Tunisia but only after the end of the war while Italy wanted them immediately. The negotiation with the Allies led to the London Pact (26 April 1915), signed by Sonnino without the approval of the Italian Parliament. According to the Pact, after victory Italy was to get Trentino and the South Tyrol up to the Brenner Pass, the entire Austrian Littoral (with Trieste), Gorizia and Gradisca (Eastern Friuli) and Istria (but without Fiume), parts of western Carniola (Idrija and Ilirska Bistrica) and north-western Dalmatia with Zara and most of the islands, but without Split. Other agreements concerned the sovereignty of the port of Valona, the province of Antalya in Turkey and part of the German colonies in Africa.

On 3 May 1915 Italy officially revoked the Triple Alliance. In the following days Giolitti and the neutralist majority of the Parliament opposed declaring war, while nationalist crowds demonstrated in public areas for it. (The nationalist poet Gabriele D'Annunzio called this period le radiose giornate di Maggio—"the sunny days of May"). Giolitti had the support of the majority of Italian parliament so on 13 May Salandra offered his resignation to King Victor Emmanuel III, but then Giolitti learned that the London Pact was already signed: fearful of a conflict between the Crown and the Parliament and the consequences on both internal stability and foreign relationships, Giolitti accepted the fait accompli, declined to succeed as prime minister and Salandra's resignation was not accepted. On 23 May, Italy declared war on Austria-Hungary. This was followed by declarations of war on the Ottoman Empire (21 August 1915,^[2] following an ultimatum of 3 August), Bulgaria (19 October 1915) and the German Empire (28 August 1916).^[3]

Italy entered into World War I also with the aim of completing national unity with the annexation of Trentino-Alto Adige and Julian March: for this reason, the Italian intervention in the First World War is also considered the Fourth Italian War of Independence,^[4] in a historiographical perspective that identifies in the latter the conclusion of the unification of Italy, whose military actions began during the revolutions of 1848 with the First Italian War of Independence.^[5][6]

The Italian Front stretched from the Stelvio Pass (at the border triangle between Italy, Austria-Hungary and Switzerland) along the Tyrolean, Carinthian, and Littoral borders to the Isonzo. Its total length was around 650 km (400 mi), of which 400 km (250 mi) ran in high alpine terrain.^[7] This information relates to measurements as the crow flies. Taking into account the natural terrain, the many yokes, peaks and ridges with the resulting differences in height, the effective length was several thousand kilometers.^[8]

The front touched very different geographical areas: in the first three sections - from the Stelvio Pass to the Julian Alps in the area of Tarvisio, it ran through mountainous territory, where the average ridge heights reached 2,700 to 3,200 meters. The higher mountainous regions have a highly rugged relief with little vegetation; Elevations over 2,500 meters are also covered by glaciers. The barren landscape and lack of sufficient arable land led to little development of these high elevations; settlement was largely limited to the lower-lying zones. From the Julian Alps to the Adriatic Sea, the mountains are constantly losing on height and only rarely reach 1,000 meters as in the area around Gorizia. This area is also sparsely populated and characterized by a harsh climate with cold winters and very hot and dry summers. A craggy karst landscape spreads out around the Isonzo valley, which adjoins the Italian foothills of the Alps in the southwest.^[9]

The topographical characteristics of the front area had a concrete impact on the conduct of the war. The rocky ground, for example, made it difficult to dig trenches and in addition, the karst rock in the Isonzo Valley turned out to be an additional danger for the soldiers. If grenades exploded on the porous surface fragments of the exploding rock acted as additional shrapnel.

Archduke Eugen, who was already in command of the Balkan forces, was promoted to Generaloberst on May 22, 1915 and was given supreme command of the new southwest front.^[10] Together with his chief of staff Alfred Krauß the 5th Army was reorganized and placed under the command of General d. Inf. Svetozar Boroević who on May 27 had arrived from the Eastern Front. The K. u. k. Landesverteidigungskommando in Tyrol (LVK) was handed to GdK Viktor Dankl to protect the Tyrolean borders. It included the German Alpenkorps which was suitable for operations in the high mountains, the first divisions arrived on May 26; a short time later, the Alpenkorps was already taking part in combat operations against Italian units, although the German Empire was not officially at war with Italy until August 28, 1916.^[11] The "Armeegruppe Rohr" stood under the command of Franz Rohr von Denta and was to secure the Carinthian front. The transfer of the 5th Army and additional troops from the east went smoothly; within a few weeks, Archduke Eugen had around 225,000 soldiers under his command. In June the 48. Division (FML Theodor Gabriel) and finally, in July, the four Kaiserjäger regiments and three k.k. Landesschützen regiments from Galicia were added. A major advantage of the Austro-Hungarian defense was its entrenchment on higher ground.

Italy ordered general mobilization on May 22, 1915 and by the end of June four armies had marched into the north-east border area. In the deployment plan of the Italian general staff (Commando Supremo) under the direction of FM Luigi Cadorna, three main points were set:

• The 1st Army was to encircle the Tyrolean front from the west and south.
• The 4th Army was to set up position in the Cadore and Carnia
• The 2nd and 3rd Armies on the other hand, were opposed to the 5th k.u.k. Army, in the Julian Alps and on the Isonzo.

Although the Italian armed forces were numerically superior, things initially remained surprisingly quiet on the southwestern front. No attempt was made to break through on the Tyrolean front, and there was no major offensive on the Isonzo either. Due to the hesitant implementation of Cadorna's attack plans, the chance to score the decisive blow right at the beginning was lost.^[12] FML Cletus Pichler, the chief of staff of the LVK Tirol, wrote: ^[13]

A general attack on the most important penetration points, such as the Stilfser Joch, Etschtal, Valsugana, Rollepass [sic], [and] Kreuzbergpass, [...] could have led to significant enemy successes in view of the extremely weak defense forces in May.

That the opportunity for a quick breakthrough was not used was partly due to the slow mobilization of the Italian army. Due to the poorly developed transport network, the provision of troops and war material could only be completed in mid-June, i.e. a month later than estimated by the military leadership.^[14] The Italian army also suffered from many shortcomings on the structural level. Artillery pieces and munitions were not the only area where shortages were acute. In August 1914 the Italian army had at its disposal only 750,000 rifles of the standard Carcano 1891 model and no hand grenades available at all. This inadequate supply of equipment especially limited the scope and efficiency of training throughout 1914 and 1915. Munitions were also urgently needed: in July 1914 only ca. 700 rounds were available per rifle, despite Cadorna's demand that 2,000 rounds each be found in preparation for war, by May 1915 the army had only succeeded in procuring 900 rounds per rifle.^[15] Meanwhile, Emilio De Bono records that "throughout 1915 hand-grenades remained unheard of in the trenches".^[16]

Italy's first machine guns were prototypes, as the Perino Model 1908, or Maxim guns acquired in 1913 from the British manufacturer Vickers. In line with the 1911 plan for creating 602 machine gun sections. By August 1914 only 150 of these had been created, meaning there was only one machine gun section per regiment, as opposed to one per battalion, as envisaged in the plans. By May 1915 the Fiat-Revelli Mod. 1914 became the standard machine gun of the Italian army and a total of 309 sections had been created, with 618 guns in total; though this was an improvement it was still only half the planned number, leaving many battalions to do without. In contrast a standard k.u.k regiment had four machine gun sections, MG 07/12 "Schwarzlose", one for each battalion, whilst a standard British regiment had by February 1915 four machine gun sections per battalion..^[17]

During the Italo-Turkish War in Libya (1911–1912), the Italian military suffered equipment and munition shortages not yet repaired before Italian entry into the Great War.^[18] At the opening of the campaign, Austro-Hungarian troops occupied and fortified high ground of the Julian Alps and Karst Plateau, but the Italians initially outnumbered their opponents three-to-one.

The first shells were fired in the dawn of 24 May 1915 against the enemy positions of Cervignano del Friuli, which was captured a few hours later. On the same day the Austro-Hungarian fleet bombarded the railway stations of Manfredonia and Ancona. The first Italian casualty was Riccardo Di Giusto.

The main effort was to be concentrated in the Isonzo and Vipava valleys and on the Karst Plateau, in the direction of Ljubljana. The Italian troops had some initial successes, but as in the Western Front, the campaign soon evolved into trench warfare. The main difference was that the trenches had to be dug in the Alpine rocks and glaciers instead of in the mud, and often up to 3,000 m (9,800 ft) of altitude.

At the beginning of the First Battle of the Isonzo on 23 June 1915, Italian forces outnumbered the Austrians three-to-one but failed to penetrate the strong Austro-Hungarian defensive lines in the highlands of northwestern Gorizia and Gradisca. Because the Austrian forces occupied higher ground, Italians conducted difficult offensives while climbing. The Italian forces therefore failed to drive much beyond the river, and the battle ended on 7 July 1915.

Despite a professional officer corps, severely under-equipped Italian units lacked morale.^[19] Also many troops deeply disliked the newly appointed Italian commander, general Luigi Cadorna.^[20] Moreover, preexisting equipment and munition shortages slowed progress and frustrated all expectations for a "Napoleonic style" breakout.^[18] Like most contemporaneous militaries, the Italian army primarily used horses for transport but struggled and sometimes failed to supply the troops sufficiently in the tough terrain.

Two weeks later on 18 July 1915, the Italians attempted another frontal assault against the Austro-Hungarian trench lines with more artillery in the Second Battle of the Isonzo. In the northern section of the front, the Italians managed to overrun Mount Batognica over Kobarid (Caporetto), which would have an important strategic value in future battles. This bloody offensive concluded in stalemate when both sides ran out of ammunition.

The Italians recuperated, rearmed with 1200 heavy guns, and then on 18 October 1915 launched the Third Battle of the Isonzo, another attack. Forces of Austria-Hungary repulsed this Italian offensive, which concluded on 4 November without resulting gains.

The Italians again launched another offensive on 10 November, the Fourth Battle of the Isonzo. Both sides suffered more casualties, but the Italians conquered important entrenchments, and the battle ended on 2 December for exhaustion of armaments, but occasional skirmishing persisted.

This stalemate dragged on for the whole of 1916. While the Austro-Hungarians amassed large forces in Trentino, the Italian command launched the Fifth Battle of the Isonzo, lasting for eight days from 11 March 1916. This attempt was also fruitless.

Following Italy's stalemate, the Austro-Hungarian forces began planning a counteroffensive (Battle of Asiago) in Trentino and directed over the plateau of Altopiano di Asiago, with the aim to break through to the Po River plain and thus cutting off the 2nd, 3rd, and 4th Italian Armies in the North East of the country. The offensive began on 15 May 1916 with 15 divisions, and resulted in initial gains, but then the Italians counterattacked and pushed the Austro-Hungarians back to the Tyrol.

Later in 1916, four more battles along the Isonzo river erupted. The Sixth Battle of the Isonzo, launched by the Italians in August, resulted in a success greater than the previous attacks. The offensive gained nothing of strategic value but did take Gorizia, which boosted Italian spirits. The Seventh, Eighth, and Ninth battles of the Isonzo (14 September – 4 November) managed to accomplish little except to wear down the already exhausted armies of both nations. The price was a further 37,000 dead and 88,000 wounded for the Italians, again for no remarkable conquest. In late 1916, the Italian army advanced for some kilometers in Trentino, while, for the whole winter of 1916–1917, the situation in the Isonzo front remained stationary. In May and June was the Tenth Battle of the Isonzo.

The frequency of offensives for which the Italian soldiers partook between May 1915 and August 1917, one every three months, was higher than demanded by the armies on the Western Front. Italian discipline was also harsher, with punishments for infractions of duty of a severity not known in the German, French, and British armies.^[21]

Shellfire in the rocky terrain caused 70% more casualties per rounds expended than on the soft ground in Belgium and France. By the autumn of 1917 the Italian army had suffered most of the deaths it was to incur during the war, yet the end of the war seemed to still be an eternity away.^[21] This was not the same line of thought for the Austro-Hungarians. On 25 August, the Emperor Charles wrote to the Kaiser the following: "The experience we have acquired in the eleventh battle has led me to believe that we should fare far worse in the twelfth. My commanders and brave troops have decided that such an unfortunate situation might be anticipated by an offensive. We have not the necessary means as regards troops."^[22]

From 1915, the high peaks of the Dolomites range were an area of fierce mountain warfare. In order to protect their soldiers from enemy fire and the hostile alpine environment, both Austro-Hungarian and Italian military engineers constructed fighting tunnels which offered a degree of cover and allowed better logistics support. Working at high altitudes in the hard carbonate rock of the Dolomites, often in exposed areas near mountain peaks and even in glacial ice, required extreme skill of both Austro-Hungarian and Italian miners.

Beginning on the 13th, later referred to as White Friday, December 1916 would see 10,000 soldiers on both sides killed by avalanches in the Dolomites.^[23] Numerous avalanches were caused by the Italians and Austro-Hungarians purposefully firing artillery shells on the mountainside, while others were naturally caused.

In addition to building underground shelters and covered supply routes for their soldiers like the Italian Strada delle 52 Gallerie, both sides also attempted to break the stalemate of trench warfare by tunneling under no man's land and placing explosive charges beneath the enemy's positions. Between 1 January 1916 and 13 March 1918, Austro-Hungarian and Italian units fired a total of 34 mines in this theatre of the war. Focal points of the underground fighting were Pasubio with 10 mines, Lagazuoi with 5, Col di Lana/Monte Sief also with 5, and Marmolada with 4 mines. The explosive charges ranged from 110 to 50,000 kilograms (240–110,230 pounds) of blasting gelatin. In April 1916, the Italians detonated explosives under the peaks of Col Di Lana, killing numerous Austro-Hungarians.

The Italians directed a two-pronged attack against the Austrian lines north and east of Gorizia. The Austrians checked the advance east, but Italian forces under Luigi Capello managed to break the Austrian lines and capture the Banjšice Plateau. Characteristic of nearly every other theater of the war, the Italians found themselves on the verge of victory but could not secure it because their supply lines could not keep up with the front-line troops and they were forced to withdraw. However, the Italians despite suffering heavy casualties had almost exhausted and defeated the Austro-Hungarian army on the front, forcing them to call in German help for the much anticipated Caporetto Offensive.

Though the last Italian offensive had proven inconclusive, the Austro-Hungarians were in strong need of reinforcements. These became available when Russia crumbled and troops from the Eastern front, the Trentino front and Flanders were secretly concentrated on the Isonzo front. On 18 August 1917 began the most important Italian offensive, the Eleventh Battle of the Isonzo. This time the Italian advance was initially successful as the Bainsizza Plateau southeast of Tolmino was captured, but the Italian army outran its artillery and supply lines, thus preventing the further advance that could have finally succeeded in breaking the Austro-Hungarian army. The Austro-Hungarian line ultimately held and the attack was abandoned on 12 September 1917.

The Austro-Hungarians received desperately needed reinforcements after the Eleventh Battle of the Isonzo from German Army soldiers rushed in after the Russian offensive ordered by Kerensky of July 1917 failed. Also arrived German troops from Romanian front after the Battle of Mărășești. The Germans introduced infiltration tactics to the Austro-Hungarian front and helped work on a new offensive. Meanwhile, mutinies and plummeting morale crippled the Italian Army from within. The soldiers lived in poor conditions and engaged in attack after attack that often yielded minimal or no military gain.

On 24 October 1917 the Austro-Hungarians and Germans launched the Battle of Caporetto (Italian name for Kobarid or Karfreit in German). Chlorine-arsenic agent and diphosgene gas shells were fired as part of a huge artillery barrage, followed by infantry using infiltration tactics, bypassing enemy strong points and attacking on the Italian rear. At the end of the first day. From Caporetto the Austro-Hungarians advanced for 150 km (93 mi) south-west, reaching Udine after only four days. The defeat of Caporetto caused the disintegration of the whole Italian front of the Isonzo. The situation was re-established by forming a stop line on the Tagliamento and then on the Piave rivers, but at the price of 10,000 dead, 30,000 wounded, 265,000 prisoners, 300,000 stragglers, 50,000 deserters, over 3,000 artillery pieces, 3,000 machine guns and 1,700 mortars. The Austro-Hungarian and German losses totaled 70,000. Cadorna, who had tried to attribute the causes of the disasters to low morale and cowardice among the troops, was relieved of duty. On 8 November 1917 he was replaced by Armando Diaz.

When the Austro-Hungarian offensive routed the Italians, the new Italian chief of staff, Armando Diaz ordered to stop their retreat and defend the fortified defenses around the Monte Grappa summit between the Roncone and the Tomatico mountains; although numerically inferior (51,000 against 120,000) the Italian Army managed to halt the Austro-Hungarian and German armies in the First Battle of Monte Grappa.

The Central Powers ended the year 1917 with a general offensive on the Piave, the Altopiano di Asiago, and the Monte Grappa, which failed and the Italian front reverted to attritional trench warfare. The Italian army was forced to call the 1899 levy, while that of 1900 was left for a hypothetical final effort for the year of 1919.

The Central Powers stopped their attacks in 1917 because German troops were needed on the Western Front while the Austro-Hungarian troops were exhausted and at the end of much longer logistical lines. The offensive was renewed on 15 June 1918 with Austro-Hungarian troops only in the Battle of Piave. The Italians resisted the assault. The failure of the offensive marked the swan song of Austria-Hungary on the Italian front. The Central Powers proved finally unable to sustain further the war effort, while the multi-ethnic entities of the Austro-Hungarian Empire were on the verge of rebellion. The Italians rescheduled earlier their planned 1919 counter-offensive to October 1918, in order to take advantage of the Austro-Hungarian crisis.

Advancing deep and fast, the Austro-Hungarians outran their supply lines, which forced them to stop and regroup. The Italians, pushed back to defensive lines near Venice on the Piave River, had suffered 600,000 casualties to this point in the war. Because of these losses, the Italian Government called to arms the so-called 99 Boys (Ragazzi del '99); the new class of conscripts born in 1899 who were turning 18 in 1917. In November 1917, British and French troops started to bolster the front line, from the 5 and 6 divisions respectively provided.^[24][25][a] Far more decisive to the war effort than their troops was the Allies economic assistance by providing strategic materials (steel, coal and crops – provided by the British but imported from Argentina – etc.), which Italy always lacked sorely. In the spring of 1918, Germany pulled out its troops for use in its upcoming Spring Offensive on the Western Front. As a result of the Spring Offensive, Britain and France also pulled half of their divisions back to the Western Front.

The Austro-Hungarians now began debating how to finish the war in Italy. The Austro-Hungarian generals disagreed on how to administer the final offensive. Archduke Joseph August of Austria decided for a two-pronged offensive, where it would prove impossible for the two forces to communicate in the mountains.

The Second Battle of the Piave River began with a diversionary attack near the Tonale Pass named Lawine, which the Italians repulsed after two days of fighting.^[27] Austrian deserters betrayed the objectives of the upcoming offensive, which allowed the Italians to move two armies directly in the path of the Austrian prongs. The other prong, led by general Svetozar Boroević von Bojna initially experienced success until aircraft bombed their supply lines and Italian reinforcements arrived.

To the disappointment of Italy's allies, no counter-offensive followed the Battle of Piave. The Italian Army had suffered huge losses in the battle, and considered an offensive dangerous. General Armando Diaz waited for more reinforcements to arrive from the Western Front. By the end of October 1918, Austro-Hungary was in a dire situation. Czechoslovakia, Croatia, and Slovenia proclaimed their independence and parts of their troops started deserting, disobeying orders and retreating. Many Czechoslovak troops, in fact, started working for the Allied Cause, and in September 1918, five Czechoslovak Regiments were formed in the Italian Army.

The Italian attack of 52 Italian divisions, aided by 3 British 2 French and 1 American division, 65,000 total and Czechoslovaks (see British and French forces in Italy during World War I), was started on 24 October from Vittorio Veneto. The Austro-Hungarians fought tenaciously for four days, but then the Italians managed to cross the Piave and establish a bridgehead, the Austro-Hungarians began to retreat and then disintegrate after the troops heard of revolutions and independence proclamations in the lands of the Dual Monarchy. Austria-Hungary asked for an armistice on 29 October. On 31 October, the Italian Army launched a full scale attack and the whole front began to collapse. On 3 November, 300,000 Austro-Hungarian soldiers surrendered, at the same day the Italians entered Trento and Trieste. The armistice was signed on 3 November at Villa Giusti, near Padua. The Italian victory^[32][33][34] which was announced by the Bollettino della Vittoria and the Bollettino della Vittoria Navale.

Italian soldiers entered Trento while Bersaglieri landed from the sea in Trieste, greeted by the population. The following day the Istrian cities of Rovigno and Parenzo, the Dalmatian island of Lissa, and the cities of Zara and Fiume were occupied: the latter was not included in the territories originally promised secretly by the Allies to Italy in case of victory, but the Italians decided to intervene in reply to a local National Council, formed after the flight of the Hungarians, and which had announced the union to the Kingdom of Italy. The Regia Marina occupied Pola, Sebenico and Zara, which became the capital of the Governorate of Dalmatia.The Governorate of Dalmatia had the provisional aim of ferrying the territory towards full integration into the Kingdom of Italy, progressively importing national legislation in place of the previous one. The Governorate of Dalmatia was evacuated following the Italo-Yugoslav agreements which resulted in the Treaty of Rapallo (1920). Italy occupied also Innsbruck and all Tyrol by the III Corps of the First Army with 20–22,000 soldiers.^[35]

Italian troops played a major role in the defence of Albania against Austria-Hungary. From 1916 the Italian 35th Division fought on the Salonika front as part of the Allied Army of the Orient. The Italian XVI Corps (a separate entity independent from the Army of the Orient) took part in actions against Austro-Hungarian forces in Albania; in 1917 they established an Italian protectorate over Albania.

Some Italian divisions were also sent to support the Entente on the Western Front. In 1918 Italian troops saw intense combat during the German spring offensive. Their most prominent engagement on this front was their role in the Second Battle of the Marne.

Italy played a token role in the Sinai and Palestine Campaign, sending a detachment of five hundred soldiers to assist the British there in 1917.

As Italy entered the war on 23 May 1915, the situation of her forces in the African colonies was critical. Italian Somaliland, in the east was far from being pacified, and in North Africa's Cyrenaica the Italian forces were confined to some separated points on the coast. But in neighbouring Tripolitania and Fezzan, the story has a different beginning. In August 1914, during their previous colonial invasion and occupation versus local military and forces of the Ottoman Empire, the Italian forces reached Ghat, that is, conquered most of western Libya. But in November 1914, this advance turned into a general retreat, and on 7 April and 28 April, they suffered two reverses at Wadi Marsit (near Mizda) and Gasr Bu Hadi (or al-Qurdabiya near Sirte) respectively. By August 1915, the situation in Tripolitania was similar to that of Cyrenaica. The conquest of all of Libya was not resumed until January 1922.

As the war came to an end, Italian Prime Minister Vittorio Emanuele Orlando met with British Prime Minister David Lloyd George, Prime Minister of France Georges Clemenceau and United States President Woodrow Wilson in Versailles to discuss how the borders of Europe should be redefined to help avoid a future European war. The talks provided little territorial gain to Italy as Wilson promised freedom to all European nationalities to form their nation-states. As a result, the Treaty of Versailles did not assign Dalmatia and Albania to Italy as had been promised. Furthermore, the British and French decided to divide the German overseas colonies into their mandates, with Italy receiving none. Italy also gained no territory from the breakup of the Ottoman Empire. Despite this, Orlando agreed to sign the Treaty of Versailles, which caused uproar against his government. The Treaty of Saint-Germain-en-Laye (1919) and the Treaty of Rapallo (1920) allowed the annexation of Trentino Alto-Adige, Julian March, Istria, Kvarner as well as the Dalmatian city of Zara.

Furious over the peace settlement, the Italian nationalist poet Gabriele D'Annunzio led disaffected war veterans and nationalists to form the Free State of Fiume in September 1919. His popularity among nationalists led him to be called Il Duce ("The Leader"), and he used black-shirted paramilitary in his assault on Fiume. The leadership title of Duce and the blackshirt paramilitary uniform would later be adopted by the fascist movement of Benito Mussolini. The demand for the Italian annexation of Fiume spread to all sides of the political spectrum.^[37]

The subsequent Treaty of Rome (1924) led to the annexation of the city of Fiume to Italy. Italy's lack of territorial gain led to the outcome being denounced as a mutilated victory. The rhetoric of mutilated victory was adopted by Mussolini and led to the rise of Italian fascism, becoming a key point in the propaganda of Fascist Italy. Historians regard mutilated victory as a "political myth", used by fascists to fuel Italian imperialism and obscure the successes of liberal Italy in the aftermath of World War I.^[38] Italy also gained a permanent seat in the League of Nations's executive council.

• Propaganda and censorship in Italy during the First World War
• Italian prisoners of war in the First World War

• Ferrari, Paolo. "The Memory And Historiography Of The First World War In Italy" Comillas Journal of International Relations (2015) #2 pp 117–126 [ISSN 2386-5776] DOI: cir.i02.y2015.009 online
• Gooch, G. P. Recent Revelations Of European Diplomacy (1940), pp 245–62 summarizes memoirs of major participants
• Gooch, John (2014). The Italian Army and the First World War. Armies of the Great War. Cambridge University Press. ISBN 978-0521149372.
• Keegan, John (2001). The first World War; An Illustrated History. London: Hutchinson. ISBN 0-09-179392-0.
• Keegan, John (1998). The first World War. London: Random House (UK). ISBN 0-09-1801788.
• Page, Thomas Nelson (1920). Italy and the World War. New York: Charles Scribner's Sons. OCLC 414372.
• Pergher, Roberta. "An Italian War? War and Nation in the Italian Historiography of the First World War" Journal of Modern History (Dec 2018) 90#4
• Pryce, Roy. "Italy and the Outbreak of the First World War." Cambridge Historical Journal 11#2 (1954): 219-27 online.

• Italy World War
• Cappellano, Filippo: Warfare 1914–1918 (Italy) , in: 1914-1918-online. International Encyclopedia of the First World War.