A Chinese communist rural base formed in 1931. Under Kuomintang attack in 1927, some communists moved to the countryside, maintaining their strength through guerrilla warfare in remote mountain regions. The group led by Mao Zedong, which first established itself on the Hunan–Jiangxi border, merged with a group led by Zhu De, and the First National Congress of the Chinese Soviet Republic was held in November 1931. Four nationalist “Encirclement Campaigns” were thwarted by guerrilla tactics between December 1930 and early 1933, but a fifth, beginning in October 1933, forced the evacuation of the Soviet and the commencement of the Long March a year later. Many communist policies, including land reform, were first tried out in the Jiangxi Soviet which, at its height, had a population of some nine million.