Which leader did not keep the promise he made at the yalta conference?

 Joseph Stalin

Details:

US president Franklin Roosevelt, British prime minister Winston Churchill, and Soviet premier Joseph Stalin, the leaders of the Allies in World War II, met at Yalta in 1945.  Churchill and Roosevelt pushed strongly for Stalin to allow free elections to take place in the nations of Europe after the war. At that time Stalin agreed, but there was a strong feeling by the other leaders that he might renege on that promise. The Soviets never did allow those free elections to occur. Later, Winston Churchill wrote, ""Our hopeful assumptions were soon to be falsified." Stalin and the Soviets felt they needed the Eastern European nations as satellites to protect their own interests.

the triple alliance. germany and austria-hungary were already allies by 1879 when, worried about a threat from russia, they formed the dual alliance. italy joined the group in 1882. there was a concern about a possible attack from france and the alliance needed powerful friends to defend it.