Unlike the other divisions of the Guardian Corps, the Cavalry isn't stationed in any one location, instead patrolling the skies of Cocoon on their airship, the Lindblum. Their usual work is disposing of the monsters roaming the uninhabited areas of the outer rim of Cocoon and other disturbances.
The Wide-area Response Brigade is a Guardian Corps unit commanded by Brigadier General Cid Raines. The brigade is more famous for its unofficial name, the "Cavalry". A mobile unit without a designated jurisdiction, the Cavalry patrols the uninhabited expanses between cities, ready to respond to emergency situations at a moment's notice. For this purpose, the brigade commands a cruiser-class airship - the sole exception in the Guardian Corps.
The Cavalry is a rebel group, loyal to the Sanctum only on the surface. The Cavalry's true intention is to subvert fal'Cie rule by toppling the Sanctum and give Cocoon to the people. The Cavalry is led by Cid Raines, with Rygdea as his right-hand man. Unknown to the rest of the Cavalry, the Sanctum fal'Cie Barthandelus makes Raines a l'Cie with a Focus to keep the recently surfaced group of Pulse l'Cie out of harm's way and following their mission.
Unaware they are being manipulated by Barthandelus, a fal'Cie who wants to destroy Cocoon, the Cavalry saves Fang from being captured by PSICOM and convince her they are on the same side: against the Sanctum. Fang agrees to help the Cavalry track down the other Pulse l'Cie as she wants to be reunited with her partner Vanille, and with her help the Cavalry captures Snow on Lake Bresha.
Now helped by both Fang and Snow, the Cavalry saves Lightning and Hope at Palumpolum and hide away Hope's father Bartholomew in a safe place. The Cavalry aids Lightning's group to infiltrate the Palamecia to rescue Sazh and Vanille.
Realizing that if he keeps on following Barthandelus's orders Cocoon will be destroyed, Cid abandons his position as the head of the Cavalry and follows his own plan: kill the Pulse l'Cie before they complete their Focus. His plan fails and he ends up being appointed as a puppet Primarch in Barthandelus's plan to drive the Cavalry into rage over their former leader's supposed betrayal.
The plan works and the Cavalry, now led by Rygdea, murder Raines and make their way to Edenhall, planning to destroy Orphan, an act they believe will free Cocoon from the fal'Cie rule. Having been lured to Orphan's Cradle, Barthandelus turns the Cavalry soldiers into l'Cie without a Focus, immediately transforming them into Cie'th.
After Cocoon has been crystallized, some Cavalry soldiers aid PSICOM and the Guardian Corps to look after the civilians. In Final Fantasy XIII-2 it is revealed that following the catastrophe, the Guardian Corps took control from the Sanctum and a provisional government was formed, consisting primarily of military personnel. The Cavalry spearheaded the administration and, seeking to rebuild society on the strength of human science and free from dependence on the fal'Cie, they founded the 'Academy.' In Final Fantasy XIII-2 Fragments Before it is revealed the Cavalry helped build the town of New Bodhum.