Side by side, the Allies and former enemy Germany together marked the 75th anniversary of one of the most important battles in World War II — the Battle of the Bulge, which stopped Adolf Hitler’s last-ditch offensive to turn the tide of the war.

At dawn on Dec. 16, 1944, over 200,000 German soldiers started the most unexpected breakthrough through the dense woods of Belgium and Luxembourg’s hilly Ardennes. Making the most of the surprise move, the cold, freezing weather and wearied U.S. troops, the Germans pierced the front line so deeply it came to be known as the Battle of the Bulge.

Initially outnumbered, U.S. troops delayed the attack enough in fierce fighting to allow reinforcements to stream in and turn the tide of the battle by Christmas. After a month of fighting, the move into Germany was unstoppable.

U.S. Secretary of Defense Mark Esper paid tribute to over 19,000 U.S. troops who died in one of the bloodiest battles in the nation’s history.