The History They Didn 't Teach You in School : Houston Indymedia

On January 7th, 1979, Vietnamese forces entered Phnom Penh and removed the
murderous Pol Pot from power, liberating Cambodia, which had been plagued
by American war and a genocidal regime over the previous decade.

The United States had facilitated the emergence of the Khmer Rouge in
Cambodia. In 1970 President Richard Nixon had become increasingly
frustrated with Cambodian leader Prince Norodom Sihanouk, who, though
technically neutral, was not preventing the Viet Cong from receiving
supplies via his territory, including the port of Sihanoukville, and
seeking refuge there from American troops. Accordingly, in March 1969, the
president began "Operation Menu"--with raids codenamed Breakfast, Lunch,
Snack, and Dinner--a series of "secret" bombings of Cambodia (secret to the
American people but not to the Cambodians being struck by them) in which
tens of thousands of sorties and hundreds of thousands of tons of bombs
would be dropped on the small country.

But Nixon still was not satisfied, so, in March 1970, the United States
helped an unpopular palindromic Cambodian politician named Lon Nol
overthrow Sihanouk. As one of his first acts, Lon Nol "invited" the
southern Vietnamese to enter Cambodia to expel VC and PAVN forces from its
territory.

Nixon, claiming that the "nerve center" of the enemy operations--the VC's
pentagon, as it were--was in Cambodia, thus authorized an invasion, or
"incursion" as he termed it, in late April, ironically just a week after
announcing the withdrawal of another 150,000 U.S. troops from Indochina.

To Nixon, the Cambodian invasion would show the world that he was tough, if
not mad, and that American credibility remained strong. As the president
explained in a televised address on 30 April, "if when the chips are down,
the world's most powerful nation acts like a pitiful, helpless giant, the
forces of totalitarianism and anarchy will threaten free nations and free
institutions throughout the world." Meanwhile the air war continued, with
U.S. pilots flying over 8,000 sorties between July 1970 and February 1971,
over 300 a day. All of Cambodia had essentially become a free-fire zone,
but, as in Laos, with little effect on the war. In both Cambodia and the
United States, however, the events of April 1970 made a huge and
long-lasting impact.

In Cambodia, a Communist rebel group, the Khmer Rouge, which had been
previously marginal, exploited the U.S.-caused terror to gain a much larger
following and, after the Lon Nol coup, joined an alliance with Sihanouk,
thereby giving it credibility. Building on the revulsion against the
United States and Lon Nol, the Khmer Rouge grew and took control of more
area throughout the early 1970s, culminating in victory in April 1975. In
power, the regime, led by Pol Pot, instituted the infamous "killing fields"
in which the Khmer Rouge eliminated perhaps a million Cambodians, by
starvation and also by execution, often for spurious reasons like speaking
French, wearing eyeglasses, or being "enemies" of the people. The
Cambodian people, in less than a decade, had to deal with the twin terrors
of the U.S. air war and the Khmer Rouge genocide.

Throughout the war, the Vietnamese communists and the Khmer Rouge
maintained cordial relations because they were both fighting against U.S.
puppet regimes. After 1975, however, the differences between the two
became intense as Pol Pot's brutal policies of de-urbanizing Cambodia was
leading to the deaths of hundreds of thousands and traditional hostilities
over land resurfaced, leading to cross-border skirmishing and then
conventional attacks.

In 1979, the Vietnamese, in what may be accurately called a humanitarian
intervention, moved on Cambodia and removed the Khmer Rouge from power,
finally giving the Cambodian people some peace after the twin horrors of
American attacks and Pol Pot's genocide.

In the aftermath of the Vietnamese liberation, the United States, in both
the Carter and Reagan administrations, continued to recognize the Khmer
Rouge as the legitimate government of Cambodia.

Further Reading:

Seymour Hersh, The Price of Power
William Shawcross, Sideshow
Michael Vickery, Cambodia
Anything by Ben Kiernan