Patrolling a province both reduces unrest and has a chance to discover hidden units. Some units are better at patrolling than others (fast units, flying units, or units with patrol bonus ). For each point of unrest eliminated in a province by patrollers, the population is reduced by 10. This represents the permanent elimination of the troublemakers. The larger the patrolling force, the more effective it is. A provincial defense level of 15 can act as a patrolling force for purposes of detecting stealthy units, but it is not as effective as an actual army. If there is no unrest in a province, nobody gets hurt by patrollers. Patrollers will fight an attacking army, just like troops given the defend province order.
The success of the Patrol order depends on the Stealth ability of the units that are hiding, their number, the provincial defense (if any), and the “Destealth strength” of the patrolling units. Destealth is affected by unrest.
Stealth strength: Stealth value of leader -1 per stealthy unit in his army (or zero if unit has >=+50 in stealth)
Destealth strength: Sum of Destealth strength of all patrolling units - unrest/2 (capped at unrest 100) + (province defence - 14 if province defence is 15 or greater)
The stealthy units are found if the Destealthy strength + 2d25 (open-ended) > Stealth strength + 2d25 (open-ended).
The individual Destealth strength of a given unit = (Precision + (AP value, or 30 if flying)) / 20.
Units with a Patrol bonus add the Patrol bonus to their individual Destealth strength.