The People's Republic of China's Great Leap Forward and other policies based on agriculture instead of heavy industry challenged the Soviet-style socialism and the signs of the USSR's influence over the socialist countries. As "de-Stalinization" went forward in the Soviet Union, China's revolutionary founder, Mao Zedong, condemned the Soviets for "revisionism." The Chinese also were growing increasingly annoyed at being constantly in the number two role in the communist world. In the 1960s, an open split began to develop between the two powers; the tension lead to a series of border skirmishes along the Chinese-Soviet border.