Pathet Lao
In October 1964, in response to an offensive by the Pathet Lao and North Vietnamese to expel the Neutralists from the Plain of Jars, the United States began providing air support against Pathet Lao positions and North Vietnamese supply lines. However, it was not until March 1966 at Phoukout, northwest of the Plain of Jars, that the Pathet Lao started to win major battles against the Royal Lao Army. In July 1966, the Pathet Lao won another major battle in the Nambak Valley in northern Louangphrabang Province by overrunning a Royal Lao Army base and inflicting heavy casualties. These victories gave the Pathet Lao new momentum in the war for control of Laos.