China's ten marshals and the first Minister of National Defense, was persecuted to death during the Cultural Revolution; he was politically rehabilitated in 1978. At the Fifth Plenum held in 1980, Peng Zhen, He Long and other leaders who had been purged during the Cultural Revolution were politically rehabilitated. Hu Yaobang became head of the Secretariat of the Chinese Communist Party as its Secretary-general. In September, Hua Guofeng resigned and Zhao Ziyang, another Deng ally, was named Premier of China. Deng remained the Chairman of the Central Military Commission, but formal power was transferred to a new generation of pragmatic reformers, who reversed Cultural Revolution policies to a large extent during the Boluan Fanzheng period. Within a few years from 1978, Deng Xiaoping and Hu Yaobang helped rehabilitate over 3 million "unjust, false, erroneous" cases in Cultural Revolution. In particular, the trial of the Gang of Four took place in Beijing from 1980 to 1981, and the court stated that 729,511 people had been persecuted by the Gang, of whom 34,800 were said to have died. In 1981, the Chinese Communist Party passed a resolution and declared that the Cultural Revolution was "responsible for the most severe setback and the heaviest losses suffered by the Party, the country, and the people since the founding of the People's Republic." Humanitarian crisis Death toll Death toll estimates from different sources vary greatly, ranging from hundreds of thousands to 20 million. In addition, the 1975 Banqiao Dam failure, considered by some as the world's greatest technological catastrophe of the 20th century, resulted in an estimated death toll between 26,600 and 240,000; the disaster, which took place during the Cultural Revolution, was covered up until at least 1989. According to Andrew G. Walder, most deaths arose after the end of the mass movement phase of the Cultural Revolution when there were organized campaigns to consolidate order in workplaces and communities. Literature reviews of the overall death toll due to the Cultural Revolution usually include the following. Massacres and cannibalism During the Cultural Revolution, massacres took place across mainland China, including: the Guangxi Massacre, in which massive cannibalism occurred; the Inner Mongolia incident; the Guangdong Massacre; the Yunnan Massacres; the Hunan Massacres; the Beijing Massacre (i.e. Red August); and the Ruijin Massacre. These massacres were mainly led and organized by local revolutionary committees, Communist Party branches, militia, and even the military. Most of the victims