During this period, the main operational form of our army was mobile warfare, and large-scale joint operations of various services and arms were gradually launched. Adapting to the change of military strategy, the engineering corps has made great progress, from dozens of companies in the early days of the liberation war to eight engineering corps companies on the eve of the founding of the People's Republic of China. Most army units have established engineering barracks, some divisions and regiments have established engineering companies and platoons, and engineering schools or engineering teaching camps and training teams have also been established in various liberated areas. Equipment was also seized and updated from the battlefield. The task of engineers has changed from participating in and supporting small-scale guerrilla warfare to ensuring the regular operations of large corps; From ensuring the actions of infantry, cavalry and artillery to ensuring that infantry, cavalry, artillery, tank soldiers, signal soldiers and other arms carry out large-scale sports attacks, attack positions and field defense; From the engineering support task of giving people away under general conditions to the engineering support task of crossing the river, resisting landing and crossing the sea.

Especially after the campaigns of Liaoshen, Huaihai and Ping Jin and the campaign of crossing the river, the engineering tactics have been developed in an all-round way, and a set of engineering tactics principles and tactics synchronized with the synthetic arms have been initially formed.