SAIGON UNITS DRIVE INTO LAOS TO STRIKE ENEMY SUPPLY LINE
thousands of S Vietnamese troops, supported by US planes and arty, cross Laotian border to strike at Ho Chi Minh Trail; Nguyen Van Thieu, announcing operation in statement, calls attack 'act of legitimate self-defense' that will be 'ltd in time as well as space'; asserts S Vietnam has no territorial ambition; US mil command emphasizes that no US ground combat troops and no US advisers will go into Laos; says US will provide arty support from S Vietnam and virtually unltd air power; attack is launched from Quangtri Prov and possibly other points; US helicopters fly S Vietnamese troops across border while S Vietnamese armored columns and infantrymen move across border on Route 9, which was cleared last wk by US troops; mil policemen prevent correspondents from crossing border; it is understood in Saigon that Nguyen Van Thieu gave Nixon right to decide on strike; Nguyen Van Thieu says his troops will withdraw when operation is finished; operation said to represent dramatic reversal of past policy; details on Nguyen Van Thieu statement; his talks with Bunker noted; US mil command justifies use of Amer support as in line with objectives of helping to protect lives of US mil personnel in S Vietnam and enhancing Vietnamization; map
