There is also a bit of the english mixed in as well, from the bill hook/halbard infantry.
The basic genesis story of the Marinian Republic is that they have excellent farmland for staple crops, grains and such, along with good lumber sources. This left them in a very unique position during a particularly vicious famine that struck the Calradia continent and allowed them to leverage their food crops at a price far in excess of what they were normally worth, and their fledgling navy allowed them to reach many markets, allowing them to maintain prices and absorb much of the wealth of all the surrounding empires for the length of the famine.
This wealth was then used to position themselves with the most powerful and effective navy on the continent and secure themselves a merchant monopoly, these naval routes were more secure, faster and allowed a greater movement of product than an equivalent land route, as well as having a powerful enough navy to muscle out any significant competitor.
This dominance of trade allows Marina to maintain a level of wealth far in excess of what it can produce as a nation from it's wood and crop industries. Marina makes it's money in the movement of goods between empires rather than the production of the goods themselves.
The Marine component of their military specilises in ship to ship combat allowing them to maintain their naval trade monopoly, so the other major powers have simply accepted that doing business through Marina is the best way to secure decent profit and trade lines.
The professional Mercenary model of their Marines means that they can maintain an army far larger than what their population would suggest as they can hire from anywhere on the continent, not just their own population, although the pay and perks of the career path make it an attractive occupation for anyone capable enough.
Marina is actually my personal favourite faction.