What was the purpose of the alliance between the nationalistsand the communists?

In October 1911, a revolt ended the Qing Dynasty and the Republic of China was founded. The leader of the revolution was Dr. Sun Yat-sen who lived from 1866 to 1925. He was the first president of the Republic of China. In order to gain support from China's workers and serfs, he formed an alliance with the Communists to end the anarchy. 

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um hi i’m new here but i have an opinion i guess. i think we are but when i say war i don’t mean fighting i mean political rallies differing opinions and cultures and ideas and they all clash so hard. not all wars are fought on a battlefield. most are fought in our minds and minds of others. somethings gonna have to change and i honestly think a ‘war’ is the best way to do it. fight it out. stand up for what you believe. it’ll work out. freakin united states of america we’ve got this.