Castro's increasing role on the world stage strained his relationship with the Soviets, now under the leadership of Leonid Brezhnev. Asserting Cuba's independence, Castro refused to sign the Treaty on the Non-Proliferation of Nuclear Weapons, declaring it a Soviet-U.S. attempt to dominate the Third World. In turn, Soviet-loyalist Aníbal Escalante began organizing a government network of opposition to Castro, though in January 1968, he and his supporters were arrested for passing state secrets to Moscow. Castro ultimately relented to Brezhnev's pressure to be obedient, and in August 1968 denounced the Prague Spring as led by a "fascist reactionary rabble" and praised the Soviet invasion of Czechoslovakia. Influenced by China's Great Leap Forward, in 1968 Castro proclaimed a Great Revolutionary Offensive, closed all remaining privately owned shops and businesses and denounced their owners as capitalist counter-revolutionaries.