 He also visited Vietnam several times for on-the-scene evaluations.Although his program of Vietnamization could be termed a success, if one considers the progress of troop withdrawals, U.S. involvement in the conflict became perhaps even more disruptive at home during Nixon's presidency than during Johnson's.The U.S. incursion into Cambodia in May 1970 to eliminate North Vietnamese sanctuaries, the renewed bombing of North Vietnam and the mining of its harbors in May 1972 in response to the North Vietnamese Easter Offensive and another bombing campaign against the North in December 1972 brought widespread protest.