Launched by Hmong tribal soldiers backed by the Central Intelligence Agency, it was based on the usage of overwhelming air power to clear the path for the guerrillas.
The guerrillas were faced with the largest concentration of Vietnamese communist troops stationed outside Vietnam, and hoped to spoil that imminent attack.
However, a communist night raid that destroyed an ammunition dump, followed by the arrival of a relief column from the 316th Division, tipped the balance of battle against the assailants.
Moreover, the communists ended their follow-up drive within ten kilometers of the Hmong main bases at Long Chieng and Sam Thong.
When France withdrew most of its military in conformity with the treaty, the United States filled the vacuum with purportedly civilian paramilitary instructors.
[2] As the Laotian Civil War flared, the Central Intelligence Agency established a secret guerrilla army in the Plain of Jars.
[3] The Royal Lao Army having been rendered essentially useless in the wake of the Battle of Nam Bac, the brunt of fighting the Laotian Civil War fell upon the Hmong guerrillas led by General Vang Pao.
These Royalist irregulars faced a formidable force equivalent to 16 battalions of enemy troops clustered around the Pathet Lao capital of Xam Neua.
These latter pressed home their undisciplined pointblank attacks with reckless courage, often returning in an aircraft holed by the backblast of their own dropped ordnance.
Because of this available airpower, Vang Pao planned to commit his guerrillas to a spoiling attack ranging out from forward bases at Nakhang and Houei Hinsa to sweep across Route 6.
[4] The Central Intelligence Agency section stationed in the American embassy believed that by disrupting the communists' expected usual dry season offensive, Vang Pao could gain the initiative in the struggle for northern Laos.
At this point, Vang Pao enlarged his spoiling attack into a full-fledged off-season offensive[7] aimed at Phou Pha Thi, dubbing it Operation Pigfat.
They found themselves with only half the U.S. air sorties planned upon, and that commitment for five days only; the brand new Operation Commando Hunt truck killing campaign on the Ho Chi Minh Trail was absorbing the rest.
On 6 and 7 December, the 11th and 12th days of Pigfat, air strikes hit Phou Pha Thi with rocketry, bombs, and napalm.
[10] On 13 December, as the available air sorties dwindled, a Hmong guerrilla company assaulted Phou Pha Thi from the southeast.
Circling Hmong attacks curled about Phou Pha Thi to both east and west; the latter cut the communist-held supply line to the ridge, Route 602.
From questioning prisoners, and from intercepted radio messages, Vang Pao learned that the enemy was also dubious of success; one of their defending battalions had lost half its manpower.
Then, as flying weather improved and air support once again increased, on 18 December the Hmong renewed their attack up Phou Pha Thi.
Vang Pao attempted to counter that by having an appeal for surrender taped by a communist prisoner; he hoped to spark mass desertion before the relief column arrived.
[9] An RLAF forward operating base at Muang Soui was stockpiled with ordnance; Thai mercenary pilots were slated to fly short strike missions from there against northerly Plain of Jars targets.
[17] Pushing down further into the Plain of Jars with their heaviest yet forces of the war, the communists bore down on the main Hmong bases of Long Chieng and Sam Thong.
General Vang Pao considered other unexpected preemptive attacks, eventually leading to Operation Off Balance six months later.