In September 1985, Pol Pot resigned as commander-in-chief of the Khmer Rouge forces in favour of Son Sen; he nevertheless continued to wield significant influence. In the summer he married a young woman named Mea; the following spring their daughter, Sitha, was born. He then travelled to Beijing to undergo cancer treatment at a military hospital, only returning to Cambodia in the summer of 1988. In 1988, the anti-Vietnamese factions entered into negotiations with the Phnom Penh government. Pol Pot deemed this too soon, for he feared that the Khmer Rouge had not gained sufficient popular support to produce significant gains in any post-war election.