The Mississippi River... It is the focus of combined efforts by the Union Army and Navy to divide the Confederacy and cut off support from western sympathizers. There are forced land marches, skirmishes, ruses on both sides, naval engagements involving the ironclads and sailing ships and the 47-day siege of Vicksburg, an important port and railroad hub for the south. The resulting losses of men, equipment and territory by the Confederacy are critical.