 Complete the following phrase:  During the MexicanAmerican War, Wood served on the staff of General Zachary Taylor, and later joined the 2nd Dragoons. During the Civil War, he participated in many battles in the Western Theater. Wood commanded a division at the Battle of Chickamauga in September 1863, during which time he chose to obey a questionable order from commanding general William S. Rosecrans to reposition his division. In doing so, Wood opened a gap in the Union lines, which contributed to the vanquishing of the Federal forces in the battle and their subsequent retreat. Wood and his division took part in the successful Union assault during the 