1972, reinforcement by Unity troops and strikes by B-52s had driven the PAVN from the high ground surrounding the valley, but they could not be pushed out of the area. General Tấn then shifted the focus of his forces to the southwest and seized Sam Thong on 18 March. The fighting around Long Tieng did not cease until 28 April. On 21 May 1972 Royal Lao and Hmong forces, supported by air strikes, attempted to retake the Plain of Jars. The fighting raged for 170 days (until 15 November), but the communists could not be evicted. PAVN and the Pathet Lao claimed to have killed 1,200 enemy troops and to have captured 80. The PAVN/Pathet Lao made additional gains during the year, but failed to overwhelm government forces. The launching of PAVN's Nguyen Hue Offensive in April 1972 had the effect of returning major American air assets to the theater and eventually increased the tempo of operations in northeastern Laos. As a result, Royal Lao armed forces, Hmong and Thai mercenaries went on the offensive, as did PAVN and the Pathet Lao, all of whom wished to become "well postured for the peace negotiations." Although there was no provision for a Laotian cease-fire written into the Paris Peace Accords signed on 27 January 1973, it had been verbally agreed between the U.S. and North Vietnamese representatives that one would be instituted within 15 days of the signing of the agreement. The fates of Laos and Cambodia were disposed of in Article 20 of the agreement, in which the North Vietnamese and the U.S. promised to respect the neutrality of both nations and to end their military intervention. Unfortunately, there was no means by which to enforce the agreement. That the North Vietnamese would uphold it, after violating two previous neutrality accords, "took optimism bordering on an act of faith that they would now abandon the ambitions and struggles of thirty years because of a clumsily drafted afterthought in a document they had no intention of honoring anyway." The Americans were pulling out of Southeast Asia as quickly as negotiations with the North Vietnamese would allow them. Ambassador Godley, stunned by the diplomatic developments, ruminated that "We had led him (Souvanna) down the garden path. Let's face it, we were cutting and running... Once we were out of Vietnam the only way we could have protected Laos was with an Army