護法運動
Chen was instrumental in backing Sun Yat-sen's Constitutional Protection Movement. He also restored Sun to power after the Guangdong-Guangxi War. Chen disagreed with Sun about the direction that reform should take—Sun wanted to unite the country by force and institute change through a centralized government based on a one-party system, while Chen advocated multiparty federalism with Guangdong becoming the model province and the peaceful unification of China. Sun became suspicious that the federalist movement was being exploited by the warlords to justify their military fiefdoms.