At 03:40 on the foggy morning of 31 January, allied defensive positions north of the Perfume River in the city of Huế were mortared and rocketed and then attacked by two battalions of the PAVN 6th Regiment. Their target was the ARVN 1st Division headquarters located in the Citadel, a three-square mile complex of palaces, parks, and residences, which were surrounded by a moat and a massive earth and masonry fortress. The undermanned ARVN defenders, led by General Ngô Quang Trưởng, managed to hold their position, but the majority of the Citadel fell to the PAVN. On the south bank of the river, the PAVN 4th Regiment attempted to seize the local MACV headquarters, but was held at bay by a makeshift force of approximately 200 Americans. The rest of the city was overrun by PAVN forces which initially totaled approximately 7,500 men. Both sides then rushed to reinforce and resupply their forces. Lasting 25 days, the battle of Huế became one of the longest and bloodiest single battles of the Vietnam War.