By 13 April, An Lộc was surrounded and under a combined artillery, armored, and infantry attack by the 9th PAVN/VC Division. PAVN forces advanced on the town through a deluge rockets, bombs, and napalm delivered by U.S. and South Vietnamese aircraft supported by massed artillery, tank, and small arms fire. Inside the town, the contingent of U.S. advisors became essential to the defense, serving as a separate staff organizing fire and air support, logistics, and intelligence. Colonel William Miller, the senior U.S. advisor, was not happy with General Hung's continuous reluctance to launch counterattacks and his reliance on U.S. air power to defeat the North Vietnamese. His hesitation and lack of motivation prompted Miller to report that: "He is tired – unstable – irrational – irritable – inadvisable – and unapproachable."