50 years ago, US troops bunkered down for the Vietnam War's most infamous siege - here's how the Battle of Khe Sanh unfolded

US Marine Corps

A US Marine Corps sniper team searches for targets in the Khe Sanh Valley

January 21 marked the 50th anniversary of the start of the Battle of Khe Sanh. The battle started with around 20,000 men from the North Vietnamese Army (NVA) fighting against some 6,000 US Marines and South Vietnamese Army soldiers.

As the battle continued, up to 45,000 US soldiers, and up to 100,000 NVA troops would take part in the brutal 77-day fight. 24,000 airstrikes dropped more than 100,000 tons of bombs - roughly 5 tons for every one NVA soldier. The NVA fired over 10,000 rockets, mortars, and artillery rounds - 360 a day on average, and 1,300 during the heaviest bombardment.

Combat was so intense that the Khe Sanh Combat Base was completely surrounded and cut off, leaving the only way to resupply the base by air.

There are still debates about the true number of casualties, but estimates range that 1,000 to 3,500 US soldiers died, and a secret report from the US Military Assistance Command, Vietnam, estimated that only 5,500 NVA troops were killed.

Both sides claimed victory; the siege was eventually broken in April of 1968 and US forces continued operations in the area after the battle, but the Khe Sanh Combat Base was destroyed, the Americans withdrew, and the McNamara Line was terminated.

Here's one of the largest and bloodiest battles of the Vietnam War unfolded over 77 days: