President Nixon, at a news conference, defends the U.S. troop movement into Cambodia, saying the operation would provide six to eight months of time for training South Vietnamese forces and thus would shorten the war for Americans. Nixon reaffirmed his promise to withdraw 150,000 American soldiers by the following spring.

The announcement that U.S. and South Vietnamese troops had invaded Cambodia resulted in a firestorm of protests and gave the antiwar movement a new rallying point. College students across the nation intensified their antiwar protests with marches, rallies, and scattered incidents of violence. About 400 schools were affected by strikes and more than 200 colleges and universities closed completely. The protests resulted in deaths at Kent State University and later at Jackson State in Mississippi.

Dissent was not limited to campus confrontations. More than 250 State Department and foreign aid employees signed a letter to Secretary of State William Rogers criticizing U.S. military involvement in Cambodia. In addition, there were a series of congressional resolutions and legislative initiatives that attempted to limit severely the executive war-making powers of the president. Senators John Sherman Cooper (R-Kentucky) and Frank Church (D-Idaho) proposed an amendment to the foreign military sales portion of a Defense Department appropriations bill that would have barred funds for future military operations in Cambodia. The bill passed in the Senate by a vote of 58 to 37, but was defeated 237 to 153 in the House. On December 29, 1970, Congress passed a modified version of the Cooper-Church Amendment barring the introduction of U.S. ground troops in Laos or Thailand.