After a three-month siege, Spanish forces under Hernán Cortés capture Tenochtitlán, the capital of the Aztec empire. Cortés' men leveled the city and captured Cuauhtémoc, the Aztec emperor.
I think the answer is the second one
<span>In 1973, the U.S. withdrew all its troops from South Vietnam; in 1975 the forces of North Vietnam captured the capital of Saigon.</span>
The Battle of Antietam was considered a turning point in the Civil War because this was the first major Union victory in the East.