his forces could only occupy half of the Plain before his offensive sputtered out at the end of July. There was also a growing public awareness in the U.S. of military activities in Laos. During October 1969, Senator Stuart Symington (D-MO) chaired hearings of the Subcommittee of the Senate Foreign Relations Committee on Security Agreements and Commitments Abroad. The testimony of subpoenaed witnesses revealed the history of U.S. involvement in the covert commitment to Laos. Due to the closed nature of the sessions and its heavily censored transcript, however, the nature and extent of that commitment was still very little understood by the American public. That changed, however, with the publication of the Pentagon Papers, which disclosed the earliest stages of Yankee Team, Barrel Roll, and the Thai commitment. President Richard M. Nixon was eventually forced to disclose the extent of U.S. participation, which further weakened ability of the U.S. to respond to the increasing PAVN and Pathet Lao threat. The spring of 1972 was not a happy one in either Washington D.C. or Vientiane. A U.S. Congressional delegation, after investigating the situation on the ground in Laos, reported that "No one we met in Laos, American or Lao, seemed to have any prescription for the future other than to continue what's being done now." Running out of resources Vietnamization was catching up with the conflict in Laos. During the 1970–1971 dry season, USAF strike missions in support of Hmong operations had dropped by 70 percent from the previous year from 114 sorties per day to 38. The grinding nature of the conflict was also having a cumulative effect on the adult male population of the Hmong. Severe attrition had forced the Hmong into a numbers game that they could not win. Although only contributing 13 percent of Laotian military strength, Vang Pao's men accounted for 70 percent of the total casualties inflicted on government forces. In March 1971 South Vietnamese forces, supported by U.S. air power, launched Operation Lam Son 719, the long-awaited offensive to cut the Ho Chi Minh trail in southeastern Laos. However, the result was a failure. PAVN and Pathet Lao forces had already begun to expand the trail system westward, pushing Royal Lao forces toward the Mekong, slowly extending the territory it controlled, moving west of the trail and creating a larger buffer zone between its logistical system and the South Vietnamese. After Lam Son