 Complete the following phrase:  Upon completion of his Vietnamese language training, Bush was assigned to the 6499th Special Activities Group, Tan Son Nhut Air Base, Saigon, Vietnam. From May 1967 to May 1968, as an Intelligence Officer, he was responsible for the deployment and operations of six intelligence teams composed of 10-15 officers and enlisted men, operating from Saigon, Bien Hoa, Nha Trang, Pleiku, Da Nang and Can Tho. The teams were involved with significant intelligence operations, particularly involving the attack on Tan Son Nhut Air Base during the Tet Offensive and the defense of the Marines and South Vietnamese at the 