The Eastern Theater Command Navy (ETCN), or the East Sea Fleet (ESF) before February 2018, is a formation of China's People's Liberation Army Navy (PLAN) and the naval component of the Eastern Theater Command.

Zhang's only previous naval experience was organizing an irregular riverine force near Hongze Lake in 1941 and leading it in a successful campaign against local bandits.

[2] The PLAN was created on 21 April when Zhang established the East China Military Region Navy, or East China Navy (ECN), with a thirteen-member headquarters,[3] and he was formally appointed by the CMC as the ECN's commander and commissar on 4 May.

The latter included Lin Zun, who defected with the ROC Navy's Second Squadron and became the ECN's, and later the ESF's, deputy commander.

By late-June, the ECN was responsible for operational and naval industrial activities along the East China Sea coastline and the Yangtze up to Jiujiang.