1947年，蒋介石悍然撕毁和平协议，对解放区发动了全面内战。《红日》这部电影生动地再现了这一历史背景下的战争场景。影片中，张灵甫率领王牌主力整编74师，奋勇向淮北发起进攻。经历了血战十二昼夜的二次攻涟水城，沈振新军长带领部队成功突围，但最终被迫败退至麦城。

然而，张灵甫并没有气馁，他连战连捷，先后攻克淮阴、宿县和临沂，向苏北和鲁南的根据地发起了进攻。他声称要在三个月内解决山东问题，并亲自活捉陈毅和粟裕。在敌强我弱的形势下，毛泽东在延安着手制定战略，并做出了关键的决策。

毛泽东将山东野战军和华中野战军合并，组建了华东野战军，以集中兵力南征北战，彻底消灭蒋介石的有生力量。这一决策成为解放战争的转折点，为中国革命的胜利奠定了坚实基础。

In 1947, Chiang Kai-shek brazenly tore up the peace agreement and launched a full-scale civil war in the liberated areas. The movie "Red Sun" vividly reproduces the war scenes under this historical background. In the film, Zhang Lingfu led the ace main force to reorganize the 74th Division and bravely launched an attack on Huaibei. After twelve days and nights of bloody battles and the second attack on Lianshui City, Army Commander Shen Zhenxin led the troops to successfully break through, but was forced to retreat to Maicheng in the end.

However, Zhang Lingfu was not discouraged. Su County and Linyi launched an attack on the base areas in northern Jiangsu and southern Shandong. He claimed to resolve the Shandong issue within three months, and personally captured Chen Yi and Su Yu alive. In a situation where the enemy is strong and we are weak, Mao Zedong started to formulate strategies in Yan'an and made key decisions.

Mao Zedong merged the Shandong Field Army and the Central China Field Army to form the East China Field Army to concentrate The troops fought south and north, completely wiping out Chiang Kai-shek's vital forces. This decision became a turning point in the War of Liberation and laid a solid foundation for the victory of the Chinese revolution.