 The proportion of slaves, however, was somewhat less than the rest of Texas.Succession as a whole, eventually led to the American Civil War, which Texas joined on the side of the Confederacy.The Battle of Galveston was fought in Galveston Bay and island on January 1, 1863, when Confederate forces under Major General John B. Magruder attacked and expelled occupying Union troops from the city, which remained in Confederate hands for the duration of the war.