A good Militaristic Policy to have if you are an expansionist bully who has serious problems with the other leaders and can't trade for additional luxury resources. Chances are you will then have enough units to station in your cities, at least when not at war. The catch is that you will need it mostly exactly when at war, due to War Weariness pulling down your general File:Amenities6.png Amenities count; so, you should separate some units to remain as garrisons and make use of Retainers, while your main army is out conquering.