Trotsky, and others, believed that the revolution could only succeed in Russia as part of a world revolution. Lenin wrote extensively on the matter and famously declared that Imperialism was the highest stage of capitalism. However, after Lenin's death, Joseph Stalin established 'socialism in one country' for the Soviet Union, creating the model for subsequent inward looking Stalinist states and purging the early Internationalist elements. The internationalist tendencies of the early revolution would be abandoned until they returned in the framework of a client state in competition with the Americans during the Cold War. With the beginning of the new era, the after Stalin period called the "thaw", in the late 1950s, the new political leader Nikita Khrushchev put even more pressure on the Soviet-American relations starting a new wave of anti-imperialist propaganda. In his speech on the UN conference in 1960, he announced the continuation of the war on imperialism, stating that soon the people of different countries will come together and overthrow their imperialist leaders. Although the Soviet Union declared itself anti-imperialist, critics argue that it exhibited tendencies common to historic empires. Some scholars hold that the Soviet Union was a hybrid entity containing elements common to both multinational empires and nation states. It has also been argued that the USSR practiced colonialism as did other imperial powers and was carrying on the old Russian tradition of expansion and control. Mao Zedong once argued that the Soviet Union had itself become an imperialist power while maintaining a socialist façade. Moreover, the ideas of imperialism were widely spread in action on the higher levels of government. Non Russian Marxists within the Russian Federation and later the USSR, like Sultan Galiev and Vasyl Shakhrai, considered the Soviet Regime a renewed version of the Russian imperialism and colonialism.