Though the Nationalists, under Sun's leadership, had allied with the Communists in the struggle against warlords, this alliance was not without tension. In November 1925, a group of right-wing Nationalist leaders met in the Western Hills and called for the expulsion of Communists from the Nationalist Party and severance of ties with the Comintern including advisor Mikhail Borodin. This manifesto was denounced by the Nationalists' party center in Guangzhou led by Chiang Kai-shek, Wang Jingwei, and Hu Hanmin, and members of the so-called Western Hills Group were either expelled or left out of the party leadership. They moved to Shanghai and regained power during the rupture between the Nationalists and Communists in April 1927.