Why did the confederates retreat from burnsides bridge

Burnside’s Bridge is a landmark in Maryland that played an important role in the Battle of Antietam during the American Civil War. In this battle, around 500 Confederate soldiers from Georgia held off repeated attacks from the Union Army for several hours.

In the third attempt by the Union Army to take over the bridge, Maj. Gen. George B. McClellan of the Union Army launched an attack against Confederate general Robert E. Lee. The battle was one of the deadliest in the Civil War, and in American history. By 5:30 on September 18, a truce was called and both sides gathered their wounded. Although the Union had had more casualties (12,410 vs. 10,316), the percentage was higher for the Confederate side (25% vs. 31%). The crippling casualties forced the Confederates to retreat across the Potomac and return to Virginia. It resulted in a strategic victory for the Union, although McClellan's overly cautious strategy was heavily criticized.

although the legal justifications for the trials and their procedural innovations were controversial at the time, the nuremberg trials are now regarded as a milestone toward the establishment of a permanent international court, and an important precedent for dealing with later instances of genocide and other crimes

you didn't list the options. however, a few communist countries today are: the people's republic of china, north korea, and cuba.