In Project Blue Ark, the apocalypse is explained. It's expected that after five-hundred years (we're still in year 100 P.A. or so) the inhabitants of earth (human and mutant) will have to fight the old, elitist humans that will, at that time, awake from their underground slumber.
Technology was not completely destroyed by the apocalyptic event in Project Blue Ark. Thanks to the heroism of one man, "Order 81" didn't go exactly according to plan. Not all of earth was destroyed, as planned by the old, elitist humans.
Thus, civilization, to varying degrees, returned. Some have primitive, tribal civilization; many have mideval civilization; and a limited few (like in France) have advanced modern civilization.
Of course, the word advanced has a new definition in the P.A. world. Steam power and metalurgy is advanced. Places like France do manufacture weaponry and ammunition. These "goods" are shipped all over the world, making some wealthy. Because these goods must be shipped (land travel is immposible in some areas of this destroyed world), pirates are also good sources of weaponry and ammunition.
A quick explanation about Savanah:
Savanah has a progresive mideval government. It is ruled by a King who has several Lords underneath him; Lord of Mammon, Lord of the City, and Lord of War. The Lord of Mammon controls the economy of Savanah; he is a rich banker of sorts. The Lord of War controls the offensive army. The Lord of the City controls the construction of embattlements and the defensive army. The power is ballance and the people are given some freedom; similar to mideval England.