Santo served as a commando within Second Platoon, specifically in B Company of the Ghost Battalion, which was a unit of the Imperial Army's Special Operations forces.
During the year 1 BBY, Santo took part in the Subjugation of Sulon. As part of First Lieutenant [Brazack]'s team, they forcefully entered the Katarn homestead with the mission of apprehending Morgan Katarn. When Koyo unlocked the workshop doors, the home droid WeeGee activated its defensive systems. The commandos used an antipersonnel grenade to disable it, and Santo silenced it permanently by blasting a hole through its speaker grill.
Because Morgan was not home, he observed the attack from a safe distance. The team went back to their base without him.