 However, consideration must be given to significant differences in terms of both military objectives and geopolitical realities between 1968 and 1972, including the impact of Nixon's recognition and exploitation of the Sino-Soviet split to gain a "free hand" in Vietnam and the shift of Communist opposition from an organic insurgency (the Viet Cong) to a conventional mechanized offensive that was by its nature more reliant on industrial output and traditional logistics.In effect, Johnson and Nixon were waging two different wars.Because of his unrelenting opposition to the Johnson administration's Vietnam policy and what was widely perceived as his hostility to Robert McNamara, LeMay was essentially forced into retirement in February 1965.