On the onset of the Belkan War, Belka seized the territory surrounding the Great Lakes as part of its advances into Osea. In the same offensive, they seized the Futuro Canal, a waterway that connected the Great Lakes to Oured Bay.
The Allied Forces launched Offensive Campaign No. 4101 to take back the canal, which in turn gave the 3rd Osean Naval Fleet access into the Great Lakes to conduct further military operations. At the conclusion of the war, the entirety of the Great Lakes was ceded to Osea.
They are the Strangereal equivalent of the Great Lakes of America.