Abstract: In assessing the military history of the Nationalist period, it is tempting to focus on the major campaigns and conflicts of the period. The Eastern Expeditions are an important yet neglected part of this history and a critical phase in the development of the Nationalist army. This article analyzes the Eastern Expeditions of 1925 in Guangdong province - the campaign against Chen Jiongming’s forces in eastern Guangdong in March, the suppression of a revolt of Yunnan and Guangxi forces in June, and the second campaign against Chen Jiongming in October and November – in order to assess their place in the development of the early Nationalist army. It argues that these 1925 campaigns served as a “defining moment” by establishing trends that would characterize the Nationalist military forces in the following decades.