The Northern Expedition
After the first KMT-CPC cooperation was established, the CPC Central Committee decided in February 1926 that the Party's main task at the time was to move the revolutionary forces northward from coastal Guangdong Province. The following summer the KMT and the CPC decided to launch the Northern Expedition and wage a war against three notorious Northern Warlords – Wu Peifu, Sun Chuanfang (1885-1935) and Zhang Zuolin (1875-1928) – who were backed by the imperialists.
On July 9, the 100,000-strong National Revolutionary Army under the Guangzhou-based National Government launched the Northern Expedition. With widespread support, the revolutionary forces spread rapidly. They took Wuchang, a city in Hubei Province, on October 10 and defeated Wu Peifu's main forces. They seized Jiujiang and Nanchang, two cities in Jiangxi Province, in November and wiped out the main forces of Sun Chuanfang. A succession of warlords in Fujian, Zhejiang and other provinces surrendered.
The Northern Expedition was proposed by the CPC and launched as a movement against warlords and occupying imperialists. In the course of the expedition, the Chinese Communists made enormous contributions both by conducting political work in the army and mobilizing the workers and peasants.
Under the command of Ye Ting (1896-1946), a Communist and a prestigious general, the Independent Regiment, composing mainly of CPC members, served as the vanguard in the Fourth Army which was renowned as "Iron Troops."
However, at a critical moment of the Northern Expedition, Chiang Kai-shek, Wang Jingwei and other KMT right-wingers launched counter-revolutionary coups in Shanghai and Wuhan. Due to Chen Duxiu's Right opportunist errors, the CPC didn't take prompt actions to deal with such a sudden incident. As a result, Chiang Kai-shek seized control of the KMT and established his rule as a new warlord. The Northern Expedition thus ended in failure.
北伐战争
第一次国共合作建立后，1926年2月，中共中央明确指出党在目前的主要任务是推动广东革命势力向北发展。1926年夏，国共两党决定进行北伐战争，其直接打击目标是受帝国主义支持的北洋军阀吴佩孚、孙传芳、张作霖三派势力。7月9日，广东国民政府领导的国民革命军10万人正式出师北伐。在各界民众的支持下，北伐军高歌猛进，于10月10日攻占湖北武昌，全歼军阀吴佩孚部主力；11月占领江西九江、南昌，并一举歼灭军阀孙传芳部主力。福建、浙江等省的军阀也纷纷倒向北伐军。
北伐战争是在中国共产党提出的反对帝国主义、反对封建军阀的口号下进行的。在北伐过程中，中国共产党人在军队、政治工作以及发动工农群众方面作出了巨大贡献。共产党员叶挺领导的、以共产党员为骨干组成的第四军独立团，成为赢得“铁军”称号的第四军中的一支英勇善战的先锋部队，叶挺也被誉为北伐名将。但是，正当北伐军向前发展的紧要关头，蒋介石、汪精卫等国民党右派势力先后在上海和武汉发动反革命政变。同时，因受陈独秀右倾机会主义错误的影响，中国共产党未能及时采取应付突发事变的正确措施。结果，蒋介石反动集团窃取了革命果实，建立了新的军阀统治，轰轰烈烈的北伐战争以失败告终。