Launched on 18 June 1969 and successful by the 27th, the assault by People's Army of Vietnam troops from the 312th Division and sappers of the 13th Dac Cong Battalion captured Muang Soui.

When France withdrew most of its military in conformity with the treaty, the United States filled the vacuum with purportedly civilian paramilitary instructors.

Invading during the opium harvest season of 1953, it settled in northeastern Laos adjacent to the border of the Democratic Republic of Vietnam.

[2] As the Laotian Civil War flared, the Central Intelligence Agency established a secret guerrilla army in the Plain of Jars.

Vang Pao had not only suffered the reverses of his failed offensives, as well as the loss of a forward airfield at Muang Soui; his defensive position was further weakened by Vietnamese communist attacks.

Faced with the looming possibility of a final guerrilla defeat, American Ambassador William H. Sullivan and Lao Prime Minister Souvanna Phouma had loosened the restrictive rules of engagement inherent in the Operation Barrel Roll bombing campaign, to little effect.

[7] An arc of militia outposts at Lima Sites served as a picket line for the guerrilla army as Vang Pao planned.

[8] However, the People's Army of Vietnam spoiled Vang Pao's plans with Operation Toan Thang (Total Victory).

[9] Previous rainy seasons had hampered PAVN mobility with muddy trails and bogged logistics; during breaks in the weather, the opposing Royalists had conducted heliborne offensive operations backed by air support.

PAVN infantry posted to the predawn attack force included the 165th Regiment of the 312th Division, as well as the sappers of the 13th Dac Cong Battalion.

By dawn, Toan Thang closed in on Neutralist Paratroop Battalion 85 at Ban Khay, where they defended Muang Soui.

[9] Thai General Phytoon Inkatanawat helicoptered into the besieged position on the 26th, as did several senior officers from the Royal Lao Army.

[9] In losing Muang Soui, Vang Pao and the Royal Lao Government had lost a hard surfaced airstrip that was extremely useful for forward staging of RLAF T-28s for strike missions.

With a record 19 battalions of PAVN in or around the Plain of Jars, well furnished with supplies by Route 7, the communists appeared able to carry out such operations as they wished.