A force of 10,000 South Vietnamese troops, supported by 200 U.S. advisers, aircraft and logistical elements, attack into what was known as the “Parrot’s Beak,” the area of Cambodia that projects into South Vietnam above the Mekong Delta. The South Vietnamese reached the town of Takeo in a 20-mile thrust. This action was part of the ongoing operation ordered by President Richard Nixon in April. U.S. and South Vietnamese forces launched a limited “incursion” into Cambodia that included 13 major ground operations to clear North Vietnamese sanctuaries 20 miles inside the Cambodian border in both the “Parrot’s Beak” and the densely vegetated “Fishhook” area (across the border from South Vietnam, 70 miles from Saigon). Some 50,000 South Vietnamese soldiers and 30,000 U.S. troops were involved, making it the largest operation of the war since Operation Junction City in 1967.

In the United States, news of the incursion set off a wave of antiwar demonstrations, including one at Kent State University that resulted in the killing of four students by Army National Guard troops. Another protest at Jackson State in Mississippi resulted in the shooting of two students when police opened fire on a women’s dormitory. The incursion also angered many in Congress who felt that Nixon was illegally widening the scope of the war; this resulted in a series of congressional resolutions and legislative initiatives that would severely limit the executive power of the president.