u.s. air force tactical strikes against north vietnam north of the 20th parallel were authorized on 5 april under the nickname "freedom train". the first large-scale b-52 raid directed against the north was conducted on 10 april when 12 b-52s, supported by 53 attack aircraft, struck petroleum storage facilities around vinh. by 12 april, president nixon had informed kissinger that he had decided on a more comprehensive bombing campaign which would include strikes against both hanoi and haiphong.