Answer:
The Allies did not give Italy the territory it had been promised for switching sides in the war.
Step-by-step explanation:
Italy joined France & Britain as the Allies in 1915 during WW1. France & Britain promised to give Italy certain Austro-Hungarian territories with large Italian populations. Italy only received some of the promised territories. The others became part of the new Yugoslavia. Italian nationalists were outraged by France & Britain's broken promises.