The General ordered the troops to advance to the fort.

Answer: Option D

Advance : move forwards in a purposeful way.
Retire : leave one's job and cease to work, typically on reaching the normal age for leaving service.
Return : come or go back to a place or person.
Escape : break free from confinement or control.
Retreat : withdraw from enemy forces as a result of their superior power or after a defeat.

Antonym of Advance is Retreat