Melvin Laird was Nixon's Defense Secretary, and prior to that he had been a Republican Congressman. He favored American troop withdrawal from Vietnam, and popularized the concept of "Vietnamization" as the shift of the burden of the fighting from the U.S. forces to the South Vietnamese Army.

Despite being the Defense Secretary, Laird was routinely bypassed in the decision-making process by Kissinger's team. His past as a Congressman made him very sensitive to public opinion, and on those grounds he opposed a large-scale U.S. intervention in Cambodia, favoring limited operations carried mainly by South Vietnam with the support of U.S. advisors.

Biography of Melvin Laird
From the U.S. Defense Department
http://www.defenselink.mil/specials/secdef_histories/bios/laird.htm