 After returning to Yan'an, Zhou Enlai was strongly and excessively criticized in this campaign.Zhou was labelled, along with the generals Peng Dehuai, Liu Bocheng, Ye Jianying, and Nie Rongzhen, as an "empiricist" because he had a history of cooperating with the Comintern and with Mao's enemy, Wang Ming.Mao publicly attacked Zhou as "a collaborator and assistant of dogmatism... who belittled the study of Marxism-Leninism".