While most of the Brotherhood's soldiers came with them from the Capital Wasteland, many inhabitants of the Commonwealth have also come under their wing; from former Gunners, to those who simply want revenge on the Institute and their synths, no matter who gets in the way.
Their ranks are (from lowest to highest): initiate, aspirant, knight, knight sergeant, knight captain, knight commander, paladin, paladin commander, star paladin, sentinel, sentinel commander and sentinel prime.
Initiates are commonly found at low levels when traversing the Commonwealth, and when the player character reaches higher levels, aspirants begin to take their place as the "low level" Brotherhood ground soldier.
Knight sergeants slowly start to replace knights in Brotherhood of Steel areas, such as checkpoints, guarding the Prydwen, Waypoint Echo, etc. They do not have the appropriate paint for their T-60 power armor, instead having common knight paint.
One of the strongest Brotherhood NPCs in the game, at early levels, they will often be found exclusively guarding the tarmac surrounding Liberty Prime in a full set of sturdy combat armor of the Brotherhood variant.
A rare and extremely deadly paladin breed, even without power armor they have deadly weaponry at their disposal, and may have several pulse or plasma grenades to disable power armor or quickly kill enemies.