On February 19, 1969, not long after Richard Nixon became President, the military command in Vietnam requested permission to commence a secret program of bombing operations within the borders of neighboring Cambodia (Shawcross, 1979, pp. 19ff). Naturally, this "secret" campaign was in no way secret from the people among whom the bombs were falling. It was "secret" only in two contexts; first, of "plausible deniability" in international diplomacy, and second probably a more important consideration of secrecy from Congressional and other opponents of the war within the United States.
The bombing of Cambodia is of broad significance in several respects. First, and most narrowly, it was an escalation of the Vietnam war, of questionable legality, in bombing the territory of a neutral nation with which the U.S. was not at war, and had no mutual security arrangements that would permit such bombing. Second, it represented the characteristic features of U.S. military policy in Vietnam, in being an application of bombing over jungle terrain in which such measures were of questionable effectiveness. Third, it added fuel to the domestic fire of angry "debate" over the conduct and morality of the Vietnam War; the failure of the bombing campaign to achieve its desired results led directly to the ground "incursion" into Cambodia, in May of 1969. This incursion in turn led immediately to the Kent State killings of four college students (not all involved in antiwar protests; one girl was merely walking across campus at some distance from the confrontation) by Ohio National Guardsmen. In turn, the increasing bitterness over the war that followed Kent State encouraged the bunker mentality within the Nixon Administration which led ultimately to Watergate.
Fourth, and most fundamentally of all, perhaps, in its human impact, the Cambodia bombing and subsequent ground incursion led to the overthrow in 1970 of the neutralist regime of Pri...