Operation Sayasila (26 July 1971—31 October 1971) was a major offensive military operation of the Laotian Civil War. It was staged by command of King Sisavang Vatthana. Launched on 26 July 1971 against the Ho Chi Minh Trail complex and its People's Army of Vietnam (PAVN) garrison, Sayasila was planned as a rather complex two phase operation dependent on coordinating two columns containing 4,400 troops with close air support in an attack on 1,100 Vietnamese Communist soldiers. When the assault stalled in mid-August, it was elaborated upon with two additional helilifts of Royalist troops behind the PAVN's mobile garrison. When the Royalist command failed to coordinate tactical movements among its various columns, the PAVN 9th Regiment moved to defeat Royalist aggressor columns one at a time.