Gunman's Peace. The Gunman Series

One hundred years after the Collapse violence still rages across the region once known as Georgia. Warlords fight for control with deadly mercenaries known as Gunmen, and Moses Prichard is one of the best. Tired of the constant turmoil he finds solace within the walls of Newlanta, a city struggling to establish an island of peace amidst the chaos. But now the city is threatened by a powerful warlord Moses once served and he is forced to strap on his guns.
However, this time he's fighting for his own reasons. Gunman's Peace, first novel of an action-packed series by Milton Davis, takes place in a post-apocalyptic world struggling to build a better future by ridding itself of the evils of the past.