The Battle of Hamburger Hill was a battle of the Vietnam War which was fought between the Unite States and North Vietnamese forces from May 10 - May 20, 1969. Although of little strategic value, US command ordered assaults to clear the area around Ap Bia, which led to pitched battles on the heavily fortified Hill 937. As the battle was primarily carried out by infantry using small arms fire, the fighting was akin to WWI trench warfare with the US Airborne troops moving up the highly sloped hill against experienced and well equipped entrenched troops. Attacks were repeatedly repelled by weather, friendly fire, accidents, and especially the highly effective North Vietnamese Army (PAVN) defenses. Nevertheless the Airborne troops took the hill through direct assault, causing extensive casualties to the PAVN forces, and taking such in their own units. The backlash due to the high casualties over a strategically unimportant point led to dramatic changes in the conduct of the war, and Hamburger Hill was the last major US ground assault of the war.