In 1861 Hatch was commissioned as a captain of the Second Iowa Cavalry. After serving at Island No. 10, he led a brigade in the Battle of Corinth and Iuka. He took part in Grierson's Raid. In December 1863, he was wounded at Moscow, Tennessee. During his recovery, he commanded the St. Louis cavalry depot. In April 1864, Hatch was promoted to brigadier general. Assigned to a division in Major General James H. Wilson's cavalry, he led troops in the Franklin and Nashville Campaign, ending his combat service there. He mustered out in 1866.
