In the Fourth Age, war was abundant. Having been in a local militia for years, he gained some experience and support from the locals. Years later from a local militia it grew to a medium army. Of course they weren't as well equiped as the state armies. Then one day Tarquinius had an idea, contraction of war. Having the resources to do so he immediately turn his army to a gear of war. To some he was a war criminal, but to others a hero.