In late 1978, the Sino-Soviet split developed into armed hostilities in Southeast Asia as war broke out between Vietnam and Kampuchea, two countries that supported the CPT. Laos, a country which hosted many PLAT bases, sided with Vietnam in the dispute. In January 1979 the CPT and PLAT were expelled from Laos by the government, a military setback for the party. Bunyen Worthong and a small section of other ex-student leaders and intellectuals broke with the party leadership and on 22 October 1979 they formed the Thai Isan Liberation Party (generally called "Pak Mai", the 'New Party') in Vientiane. "Pak Mai" was a communist party that supported Vietnamese-Laotian positions and was based in Laos.