Cavalry: a group or fighters (soldiers, warriors, etc) mounted on horses
The foot soldiers will follow the cavalry into the valley.
The foot soldiers will follow the cavalry into the valley.
Calvary: the Crucifixion place for Jesus; also used to refer to crucifixion crosses and sites in general or to describe intense pain
The pilgrims went to Calvary in Jerusalem.
Unless you write or read a lot of Christian materials, you probably won’t come across Calvary so learning to spell cavalry alone may be enough!