The army also incorporated elements of the former Manchurian occupation forces, which included around 30 thousand Japanese technicians.

[1] The army was commanded by Lin Biao, and it was involved in many crucial battles including the Liaoshen Campaign.

[citation needed] After the fall of Tianjin to Communist forces on 14–15 January 1949, the Nationalist garrison in Beiping was effectively isolated.

On 31 January 1949, the Fourth Field Army entered Beiping to take over the city which marked the conclusion of the Pingjin Campaign.

[9] The Fourth Field Army fought in the Bobai Campaign (November–December 1949), and on May 1, 1950, elements, including the 45th Corps, completed the Landing Operation on Hainan Island.