During the second day of fighting at Gettysburg the 1st Minnesota Regiment was ordered to charge the the advancing Confederates in order to provide more time for reinforcements to arrive. If the Confederates were successful, the Union line would be broken and the battle won. Greatly outnumbered the 262 men charged. As it says on the memorial at Gettysburg:
The 83% casualty rate is the largest loss by any surviving unit in American History.