This is one of the Policies that could be called "permanent," because it is always useful in any game situation. It works by reducing the effective Gold maintenance fee of each unit you've got by 1. Since maintenance is an automatic expense, this Policy reduces or even eliminates this expense - units up to the Renaissance Era only have a maintenance of 1, which means that they will become free! The resulting savings may be utilized any way you decide, and that's what makes this Policy so ubiquitously useful. Usually you should have it in a Military slot at all times, unless you have other overriding goals at the moment, such as the need to enlarge your army or fight off enemy invasions.
Civilopedia entry Edit
Military conscription is found in most ancient civilizations without professional armies (distinguished from the ilkum and corvee systems, which tended to be devoted to more pacific activities). Rather, levies of more-or-less able-bodied and more-or-less trained “recruits” were necessary in times of unrest. Although armament and ability varied considerably, such levies generally fought as infantry under their king or his designates. However, early wars didn’t last long; it was in everyone’s interest to get the battles over with in time for harvest, as most of the conscripts were farmers. But, at least, they were cheap.