Prior to the summer of 1914, Italy had been an ally of Germany and Austria-Hungary, as a member of the so-called Triple Alliance since 1882. When war broke out, however, Italy declared itself neutral and remained strictly so until the spring of 1915. All this time, Italy watched the war develop and calculated how to reap the greatest benefit from the situation.
In April 1915, Italy approached Austria-Hungary and offered its alliance to the Central Powers in exchange for a list of a half-dozen territories under Austrian control. When Austria refused a few days later, Italy turned to the Allied Powers with an even longer list of demands. Negotiations began immediately, and a few weeks later, on April 26, a secret agreement was signed that came to be known as the London Pact. The pact granted Italy claims to territories in Austria-Hungary, as well as in Albania, Turkey, and North Africa. Thus, on May 23, 1915, Italy declared war on Austria-Hungary.
Italian forces promptly advanced into the mountainous border regions of South Tyrol and to the Isonzo River. They made good progress at first, but within weeks, the front bogged down in the treacherous terrain, while the Austro-Hungarian forces pulled off a very effective defense. As a result, one more entrenched front line was added to the war.
The Italians and Austrians fought battle after battle along the Isonzo River, and though losses were huge, progress by either side was negligible. The situation continued largely unchanged until the Italians were defeated in the disastrous Battle of Caporetto in October 1917 and forced to retreat from the area. A combined total of 750,000 casualties were lost on both sides during two and a half years of fighting in which nothing substantial was accomplished.
During the stalemate between Italy and Austria-Hungary, one of the longest and most catastrophic battles of the war was fought several hundred miles away, in France. On February 21, 1916, Germany launched an offensive against the fortified French town of Verdun, which guarded the approach to Paris. The Germans intended to make a sustained attack that would drain the enemy of soldiers and force a break in the stalemate. Both sides employed shells filled with poison gas on a large scale. France temporarily lost Verdun and its two forts but regained the forts by battle’s end and recaptured the town in a renewed attack that ended the battle on December 18. After ten months, the fighting ceased, with both sides back where they had started but with a staggering 650,000 soldiers dead. The Battle of Verdun was the longest single battle of the war, and among the deadliest.
On July 1, 1916, even as the fight was still raging at Verdun, Allied Powers launched an offensive of their own along a twenty-five-mile front that extended across both banks of the river Somme. The opening artillery barrage was so heavy that it could be heard in southern England. During the four-and-a-half-month Battle of the Somme, the Allies managed to make a small advance of only six miles, at a cost of 146,000 lives. The German death toll was 164,000.