VIETNAMESE MARINES AND THE COMMUNIST INSURGENCY 43

the official restrictions under which most U.S. military advisors had operated since 1955. One important change would allow all advisors to accompany their Vietnamese units into combat. At the same time President Kennedy decided against ordering U.S. ground forces into the war zone; however, he instructed the Secretary of Defense,Robert S. McNamara, to prepare plans for such a contingency. He also approved General Taylor's recommendation that American helicopter units be sent to support the RVNAF. The arrival of first of these reinforcements just before 1961 ended, signalled the beginning of a new and more dynamic phase of American military participation in the struggle to preserve the independence of South Vietnam.