When the Union forces controlled the Mississippi River, it ruined the chances of the Confederacy winning. One of the reasons why it ruined the Confederates chances was because the Mississippi River was the water route that the Confederates used in order to send supplies and soldiers. This meant they could no longer get new supplies to the Confederate soldiers. Along with this, it split the Confederacy in half. This meant that the Confederate soldiers in different states could not communicate very easily.