had instructed Dũng not to target the airlift itself. Meanwhile, members of the police in Saigon had been promised evacuation in exchange for protecting the American evacuation buses and control of the crowds in the city during the evacuation. Although this was the end of the American military operation, Vietnamese continued to leave the country by boat and, where possible, by aircraft. RVNAF pilots who had access to helicopters flew them offshore to the American fleet, where they were able to land. Many RVNAF helicopters were dumped into the ocean to make room on the decks for more aircraft. RVNAF fighters and other planes also sought refuge in Thailand while two O-1s landed on . Ambassador Martin was flown out to the , where he pleaded for helicopters to return to the embassy compound to pick up the few hundred remaining hopefuls waiting to be evacuated. Many Vietnamese nationals who were evacuated were allowed to enter the United States under the Indochina Migration and Refugee Assistance Act. Decades later, when the U.S. government reestablished diplomatic relations with Vietnam, the former embassy building was returned to the United States. The historic staircase that led to the rooftop helicopter pad in the nearby apartment building used by the CIA and other U.S. government employees was salvaged and is on permanent display at the Gerald R. Ford Museum in Grand Rapids, Michigan. Final assault In the early hours of 30 April, Dũng received orders from the Politburo to attack. He then ordered his field commanders to advance directly to key facilities and strategic points in the city. The first PAVN unit to enter the city was the 324th Division. By now, the government had not made any sort of appeals to the people for donations of blood, food, etc. On the morning of 30 April, PAVN sappers attempted to seize the Newport Bridge but were repulsed by the ARVN Airborne. At 09:00 the PAVN tank column approached the bridge and came under fire from ARVN tanks which destroyed the lead T-54, killing the PAVN Battalion commander. The ARVN 3rd Task Force, 81st Ranger Group commanded by Major Pham Chau Tai defended Tan Son Nhut and they were joined by the remnants of the Loi Ho unit. At 07:15 on 30 April, the PAVN 24th Regiment approached the Bay Hien intersection () 1.5 km from the main gate of Tan Son Nhat Air Base.