Brother Battle Auxiliaries
This material here also applies (though to a lesser extent) to tertiaries, lay clerks and the like - the lay brothers and sisters of other sects.
The Brother Battle, like most monastic orders, have a series of householders and lay brothers who assist them in things beneath the dignity of a full brother. Householder stewards see to Brother Battle estates, lay brothers sweep and clean the fortress-monasteries, lay clerks tabulate for adept-administrators and so forth. Some of these lay brethern have made minor monastic professions, and others are purely secular - partly a personal choice and partly a question of the importance of their role, with the more important lay clerks and householders more likely to have professed as lay brothers.
At their core, the Brother Battle are soldiers, however - and so the most revered of their lay brethern are those who bear arms for the Order, the Brother Battle Auxiliaries. Auxiliaries are essentially Brother Battle armsmen, soldiers trained by the Order who take minor monastic vows to serve in their military as men at arms. In return, the Order pays them and their families, trains them and arms them, much like the soldiers of a house or other sect - though the Auxiliaries are expected to serve a religious cause, and thus are held to higher standards of conduct than a Hawkwood or Hazat armsmen might.
As soldiers, auxiliaries wear uniforms, live in barracks, have regular duties to train and parade and stand guard and, of course, attend services and pray. Auxiliaries are usually (but not always) posted near their homes and families, and those auxiliaries who are married or have children may receive dispensation after some years of service to live outside the monastery with their families. Auxiliaries in war zones, however, are kept in barracks for safety and ease of muster - they are soldiers first. This military purpose means that they operate in units (squads, troops, companies and so on) follow chains of command and so forth and so on.
Like other soldiers, auxiliaries can muster out once their term of service is done, though it is less common than among secular soldiers - after they can no longer fight, auxiliaries are still lay brothers, and so the Order puts them to work in non-combat roles or finally retires them to a quiet priory somewhere, usually one run by another sect as the Brother Battle monasteries are too geared towards war. If an auxiliary musters out, they are released from their vows amicably, and former auxiliaries often become valued members of House or mercenary units due to their Brother Battle training, though at the same time their loyalty is always suspect.
Auxiliaries who go AWOL, on the other hand, are treated as deserters and punished typically with swift death. More than other deserters, deserting auxiliaries are in danger - there are Brother Battle on every world, all subject to the same jurisdiction, so a deserter cannot escape their former masters by fleeing to the domain of another House (or in the case of other Church soldiers, diocese.)