President ??? said last night in a nationally ??? speech that American and ??? Vietnamese troops have cro??? the Cambodian border to attack ??? central Vietcong base complex, ??? lies 20 miles into Cambodian ???tory.

About ??? helicopter-borne troops of the ??? Cavalry Division, supported ??? B-52 raids and South Vietname ??? troopers, entered Cambodia at ???ximately 7 p. m. Eastern Daylight ???, two hours before the President's ??? and one hour before his conference with Congressional leaders. ???ction was the first use of American ???ound troops against Communi ??? in Cambodia.

After ??? that "the actions of the enemy in ??? ten days clearly endanger ??? of Americans who are in Vietnam??? and would jeopardize the succe??? his Vietnamization program, ??? aid, "I have concluded the time ??? for action."

Pointing ??? map, Nixon said that the new operation would be aimed at "cleaning out" Communist sanctuaries on the "Fishhook" corridor, which extends along the border about 70 miles northwest of Saigon. The primary target is the headquarters of the Central Office for South Vietnam (COSVN), the Communist base directing the South Vietnamese war effort.

"This is not an invasion of Cambodia," Nixon said. "The areas in which these attacks will be launched are completely occupied and controlled by North Vietnamese forces. Our purpose is not to occupy the area."

Nixon only briefly mentioned Cambodia's request for massive assistance, which, he said, "could not be rapidly and effectively utilized against the immediate threat." The solution, he said, was "to go to the heart of the trouble" by destroying Communist sanctuaries, noting that some of these "are as close to Saigon as Baltimore is to Washington."

In a comment apparently directed towards the Soviet Union and Communist China, Nixon said, "These actions are in no way directed at thesecurity interests of any nation."

No Pretext

"Any government that chooses to use these actions as a pretext for harming relations with the United States will be doing so on its own responsibility and at its own initiative." he continued. " and we will draw the appropriate conclusions."

Discussing possible political repurcussions of his action, Nixon said he had "rejected all political considerations in making this decision."

"I would rather be a one-term President than be a two-term President at the cost of seeing America become a second-rate power and seeing this nation accept the first defeat in its proud 190-year history." Nixon said.

The operations begun Wednesday in the "Parrot's Beak" region of southern Cambodia-described by Nixon as "exclusively South Vietnamese ground operations, under South Vietnamese command. with the United States providing air and logistical support"-will continue Nixon did not commit troops to the central area of Cambodia, which is also involved in conflict.

Smaller Footsteps

Comparing his decision to those made by Presidents Wilson. Franklin Roosevelt, Eisenhower, and Kennedy, Nixon said his own was "not of the same magnitude.

However. he said, "In these decisions, the American people were not assailed by counsels of doubt and defeat from some of the most widely-known opinion leaders of the nation."

The decision to attack the COSVN headquarters is considered a victory for American military commanders, who for five years have requested permission to launch operations against the Communist base complex.

Great Institutions

Near the end of his speech. Nixon said, "We live in an age of anarchy both abroad and at home." Referring to "mindless attacks on all the great institutions [of] free civilizations," Nixon said. "Even here in the United States great universities are being systematically destroyed."