This is one of the Policies that could be called 'permanent', because it is always useful in whatever game situation. It works by reducing the effective File:Civ6Gold.png 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 at all times in a Military slot, unless you have other overriding goals at the moment, such as the need to enlarge your army or fight off enemy invasions.