This cutting edge study examines the career of Chinese politician and diplomat Zhou Enlai (1898–1976) and assesses his leadership role in the Communist Party of China’s (CPC) strategy against the Japanese invasion of China which established the foundation for post-World War II Sino-Japanese relations. It considers how Zhou dealt with Japanese imperialism during his midcareer, from the May Fourth Movement to the formation of the second United Front between the Chinese Nationalist Party (KMT) and the CPC against Japan, which paved the way for the Chinese victory in the second Sino-Japanese War. Addressing significant moments such as the Manchurian Incident and the Xi’an Incident, it provides a thought-provoking reexamination of Zhou’s involvement in the May Fourth Movement of 1919, the first national grassroots movement in the modern history of China calling for anti-imperialism and nationalism, and also of his time in Europe, as essential background to understand the birth of the CPC and Zhou’s role in it, as well as Zhou's collaboration with Zhang Xueliang, the culprit of the Xi'an Incident. Through an in-depth analysis of primary sources, including Zhou’s own writings, the oral history of Chinese officials, and newly declassified diplomatic archives, this work presents a comprehensive and accurate account of Zhou’s career against the backdrop of Japanese imperialism.