1969 To 1973
During the June 1969 rainy season, the Pathet Lao and two North Vietnamese battalions, using Soviet tanks, pushed the Royal Lao Army and the Neutralists out of their base at Muang Sua northwest of the Plain of Jars. Fighting continued during the monsoon season. In September 1969, Vang Pao's Hmong, supported by United States bombing, launched a series of surprise attacks against key points on the Plain of Jars. A new North Vietnamese army division joined the battle shortly thereafter and by February, 1970, had regained all of the devastated plain.
In 1970, despite eight years of ground offensives by the Royal Lao Army and massive United States air support, the Pathet Lao had grown into an army of 48,000 troops and was prepared to challenge Royal Lao Army forces on their own territory by mounting large offensives in the south, engaging an even greater number of North Vietnamese forces. The introduction of Soviet-made long-range 130mm artillery pieces onto the battlefield, in that year, allowed the Pathet Lao and North Vietnamese to neutralize to some extent the Royal Lao Army's advantage of air superiority.
In 1970 the combat elements of the Royal Lao Army were organized into fifty-eight infantry battalions and one artillery regiment of four battalions. The largest tactical unit was the battalion, which was composed of a headquarters, a headquarters company, and three rifle companies. Royal Lao Army units were devoted primarily to static defense and were stationed near population centers, lines of communication, depots, and airfields. These units were complemented by military police and armored, engineer, and communications units. Between 1962 and 1971, the United States provided Laos with an estimated US$500 million in military assistance, not including the cost of equipping and training irregular and paramilitary forces. During the 1971-75 period, it added about seventy-five T-28 light-strike or training aircraft, about twenty C-47s in both transport and gunship configurations, fewer than ten H-34 helicopters, and some small U-1 and U-17 aircraft.
In February 1971, a major offensive by the South Vietnamese army, with United States logistical and air support, sent two divisions into Laos in the vicinity of Xépôn, with the objective of cutting North Vietnamese supply lines. However, once inside Laos, South Vietnamese commanders were separated from their resupply bases by long logistics lines, resulting in an early termination of the offensive. By December 1971, the Pathet Lao had taken Paksong on the Bolaven Plateau and had invested the main Hmong base at Longtiang. Communist advances continued into 1972 and encircled Thakhek on the Mekong, and Vientiane.
The cease-fire of February 22, 1973, ended bombing by the United States and temporarily halted ground offensives. The Pathet Lao, however, following their usual practice, used the cessation of military operations to resupply their forces over the long and exposed roads from North Vietnam. In further fighting in the spring of 1975, the Pathet Lao finally broke the resistance of Vang Pao's Hmong blocking the road junction linking Vientiane, Louangphrabang, and the Plain of Jars. Watched by two battalions of Pathet Lao troops, which had been flown into Vientiane and Louangphrabang on Soviet and Chinese planes to neutralize those towns under the cease-fire agreement, the communists organized demonstrations to support their political and military demands, leading to the final, bloodless seizure of power in the towns that the RLG had held until then.