Josip Broz Tito
The event was significant not only for Yugoslavia and Tito, but also for the global development of socialism, since it was the first major split between Communist states, casting doubt on Comintern's claims for socialism to be a unified force that would eventually control the whole world, as Tito became the first (and the only successful) socialist leader to defy Stalin's leadership in the COMINFORM. This rift with the Soviet Union brought Tito much international recognition, but also triggered a period of instability often referred to as the Informbiro period. Tito's form of communism was labeled "Titoism" by Moscow, which encouraged purges against suspected "Titoites'" throughout the Eastern bloc.

Q: What name refers to the period of instability during the rift between Tito and the USSR?
Informbiro