Battles of the Isonzo


The Battles of the Isonzo were a series of twelve battles between the Austro-Hungarian and Italian armies in World War I mostly on the territory of present-day Slovenia, and the remainder in Italy along the Isonzo River on the eastern sector of the Italian Front between June 1915 and November 1917.

Italian military plans

In April 1915, in the secret Treaty of London, Italy was promised by the Allies some of the territories of Austro-Hungarian Empire which were mainly inhabited by ethnic Slovenes, Croats and Austrian Germans.
Italian commander Luigi Cadorna, entering the war with the belief that a frontal assault would achieve a breakthrough, opted for an offensive on the Isonzo river. He initially planned to capture the main Italian objectives on the east and break onto the Slovenian plateau, taking Ljubljana and threatening Vienna. However, the conflict evolved into a type of trench warfare similar to the Western Front. The area between the northernmost part of the Adriatic Sea and the sources of the Isonzo River thus became the scene of twelve successive battles between 1915 and 1917.
As a result, the Austro-Hungarians were forced to move some of their forces from the Eastern Front and a war in the mountains around the Isonzo River began.

Geography

The long Soča River at the time ran entirely inside Austria-Hungary in parallel to the border with Italy, from the Vršič pass in the Julian Alps to the Adriatic Sea, widening dramatically a few kilometers north of Gorizia, thus opening a narrow corridor between Northern Italy and Central Europe, which goes through the Vipava Valley and the relatively low north-eastern edge of the Postojna Gate to Inner Carniola and Ljubljana.
Italian troops did not reach the port of Trieste, the Italian General Luigi Cadorna's initial target, until after the Armistice.

Primary sector for Italian operations

With the rest of the mountainous length of the front being almost everywhere dominated by Austro-Hungarian forces, the Soča was the only practical area for Italian military operations during the war. The Austro-Hungarians had fortified the mountains ahead of the Italians' entry into the war on 23 May 1915.
Italian Chief of Staff Luigi Cadorna judged that Italian gains were most feasible at the coastal plain east of the lower end of the Soča River. Cadorna had not expected operations in the Isonzo sector to be easy. He was well aware that the river was prone to flooding—and indeed there were record rainfalls during 1914–1918. Further, when attacking further north the Italian army was faced with something of a dilemma: in order to cross the Isonzo safely it needed to neutralise the Austro-Hungarian defenders on the mountains above, yet to neutralise these forces the Italian forces needed first to cross the river.

Casualties

Despite the huge effort and resources poured into the continuing Isonzo struggle, the results were invariably disappointing and without real tactical merit, particularly given the geographical difficulties that were inherent in the campaign.
Cumulative casualties of the numerous battles of the Isonzo were enormous. Half of the entire Italian war death total – some 300,000 of 600,000 – were suffered along the Soča River. Austro-Hungarian losses, while by no means as numerous, were nevertheless high at around 200,000.
More than 30,000 casualties were ethnic Slovenes, who at the time were citizens of Austria and thus, the majority of them served in the Austro-Hungarian Army, while Slovene civilian inhabitants from the Gorizia and Gradisca region also suffered in many thousands because they were resettled in refugee camps. These Slovene refugees were treated as state enemies in Italian refugee camps, where thousands died of malnutrition.

Number of battles

With almost continuous combat in the area, the precise number of battles forming the Isonzo campaign is debatable. Some historians have assigned distinct names to a couple of the Isonzo struggles, most notably at Kobarid in October 1917, which would otherwise form the Twelfth Battle of the Isonzo.
The fact that the battles were always named after the Isonzo River, even in Italy, was considered by some a propaganda success for Austria-Hungary: it highlighted the repeated Italian failure to breach this landmark frontier of the Empire.
The Isonzo campaign comprised the following battles:
BattleDatesItalian casualtiesAustro-Hungarian casualtiesOutcome
First Battle of the Isonzo23 June – 7 July 191515,00010,000Inconclusive
Second Battle of the Isonzo18 July – 3 August 191541,80046,600Italian victory
Third Battle of the Isonzo18 October – 3 November 191566,99841,847Austro-Hungarian victory
Fourth Battle of the Isonzo10 November – 2 December 191549,50032,100Italian victory
Fifth Battle of the Isonzo9–15 March 19161,8821,985Inconclusive
Sixth Battle of the Isonzo6–17 August 191651,00042,000Italian victory
Seventh Battle of the Isonzo14–18 September 191617,00015,000Italian victory
Eighth Battle of the Isonzo10 October 1916 – 12 October 191655,00038,000Inconclusive
Ninth Battle of the Isonzo31 October – 4 November 191639,00033,000Austro-Hungarian victory, Italian advance halted
Tenth Battle of the Isonzo10 May – 8 June 1917150,000125,000Limited Italian advance
Eleventh Battle of the Isonzo18 August – 12 September 1917158,000115,000Italian victory
Twelfth Battle of the Isonzo24 October – 19 November 1917305,00070,000Austro-Hungarian-German victory; end of the Isonzo Campaign
Total casualtiesJune 1915 – November 1917950,180570,532Central Powers victory, counteroffensives on the Piave river

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