Battle of Xuân Lộc
Once Xuân Lộc fell on 21 April 1975 , the PAVN battled with the last remaining elements of III Corps Armored Task Force , remnants of the 18th Infantry Division and depleted Marine , Airborne and Ranger Battalions in a fighting retreat that lasted nine days , until they reached Saigon and PAVN armored columns crashed throughout the gates of South Vietnam's Presidential Palace on 30 April 1975 , effectively ending the war . 
<triplet> ending the war <subj> 30 April 1975 <obj> point in time