On 20 August 1971, Lon Nol (now president) launched Operation Chenla II in an effort to open communications between Phnom Penh and the nation's second largest city, Kompong Thom. The two cities had been isolated from another for more than a year by the Khmer Rouge. FANK was initially successful, but the Khmer Rouge backed by the PAVN launched a counteroffensive and annihilated the government forces. By the end of the year the government was facing approximately 40,000 Khmer Rouge, who had taken on most of the ground fighting against the government.