Italy entered World War I in May of 1915, bringing its conscript army in on the side of the Triple Entente (England, France, and Russia) partly on the basis of promises made by the allies. The Italian army eventually grew to five million men and had more equipment in the field than did the British. The Italians fought bravely but for two years the Italian front, like the Western front, was mired in trench warfare. Italian forces eventually had to retreat to the Piave River after taking massive casualties in the battle of Caporetto. In 1918 the Italians counter-attacked with help from Britain and France. Losses on both sides were high, but the Italians were eventually victorious in the battle of Vittorio Veneto. Austria sued for peace, and an armistice was signed on the Italian front on November 3rd, 1918. The Italian celebration of its victory at Vittorio Veneto and in the war was on the next day, September 4. The overall armistice that ended all fighting in Europe was signed a week later.
Over 650,000 Italian troops were killed during the war, and a further one million injured. The cost of the war had left Italy almost bankrupt, its national debt rising from 16 to 85 billion Lire. The government eventually resorted to printing money, causing massive inflation, similar to that seen in Germany in the Î30s. Savings were destroyed, and there was mass unemployment when the soldiers came back into the civilian side of the economy. Italy expected the promised assistance in making up its wartime losses.
But Italy was sorely disappointed and, eventually, angry over its treatment in the peace settlement. Italy's allies failed to keep their territorial and economic promises, and what little land Italy received was economically unproductive. Italians felt all their efforts had led to a "Mutilated victory", and that "the peace was not worth the war." They also muttered about being treated the same way as the losers were treated.
And so Italy has always commemorated separately its own victory and armistice on November 4.