Because of his outstanding talent and sharp writing style, he won the appreciation and admiration of patriotic general Fu. 1in the spring of 939, Fu personally appointed him as a confidential secretary and concurrently served as the director of the executive agency (equivalent to the political department), responsible for the ideological propaganda and political mobilization of the Anti-Japanese War. Yan Youwen was called Fu's "right-hand man" and won Fu's trust. During the period, he kept in mind the party's 16 policy of "keeping a low profile, lying in ambush for a long time, accumulating strength and waiting for the opportunity" and buried himself in his work.

At the beginning of the war of liberation, Yan Youwen made a detailed report on Fu's strength and operational intention, as well as the contradiction between Fu and Jiang, which played an important role in preventing the North China People's Liberation Army from further losses in the Suidong campaign.

1948 10 before the northeast field army entered the customs, at the request of the central intelligence minister Li Kenong, it took Yan Youwen only 10 days to inform the central authorities of the details of Fu's battle plan. This information played an important role in the strategic deployment of the Central Military Commission for the Battle of Ping Jin. Intelligence shows that Fu's 600,000 troops may retreat from Suiyuan in the west, or from Tianjin, Tanggu and Jiang Huishi in the south. Therefore, the central government decided to launch the battle of Ping Jin in advance, and cut off Fu Jun's retreat in the west and south immediately after the Northeast Army entered the customs.

194865438+February, Li Kenong repeatedly instructed Yan Youwen to keep abreast of Fu's movements and seize the opportunity to do some work that affected Fu. 1949 1 year1October 2 1 day, entrusted by Fu, Yan Youwen discussed the plan for the peaceful liberation of Peiping with Fu and two representatives of the People's Liberation Army, and drafted the Agreement on the Peaceful Settlement of the Peiping Problem. Yan Youwen, a hidden soldier, made great contributions to the peaceful liberation of Peiping.

After the liberation of Peiping, Yan Youwen's true identity has not been made public due to the need of work and the arrangement of the central authorities. For many years, he has been risking his life to secretly engage in "underground" work, which has made great contributions to the cause of liberation, but his deeds and identity have never been made public. Until Yan Youwen died in 1962, few people knew his heroic deeds, even his children knew nothing about it.