The Civil War in OhioAfter General Ambrose E. Burnside issued General Order Number 38 in early 1863, warning that the "habit of declaring sympathies for the enemy" would not be tolerated in the Military District of Ohio, Vallandigham gave a major speech charging the war was being fought not to save the Union, but to free blacks and enslave whites. Burnside ordered his arrest and took Vallandigham to Cincinnati for trial. At the trial, Vallandigham was found guilty. The court sentenced him to prison for the duration of the war. President Lincoln attempted to quiet the situation by writing the Birchard Letter, which offered to release Vallandigham if several Ohio congressmen agreed to support certain policies of the Administration. To try to prevent political backlash and preserve authority of Gen. Burnside, Abraham Lincoln changed Vallandigham's sentence to banishment to the South. The threat was imprisonment if Vallandigham returned to northern soil. The South allowed Vallandigham to migrate to Canada where he remained for the duration of the war. He campaigned for governor in 1863 against Brough which bitterly divided much of southern Ohio.
Ohio raised nearly 320,000 soldiers for the Union army, third behind only New York and Pennsylvania in total manpower contributed to the military. Of these, 5,092 were free blacks. Ohio had the highest percentage of population enlisted in the military of any state. Sixty percent of all the men between the ages of 18 and 45 were in the service. Ohio mustered 230 regiments of infantry and cavalry, as well as 26 light artillery batteries and 5 independent companies of sharpshooters. Total casualties among these units numbered 35,475 men, more than 10% of all the Buckeyes in uniform during the war. There were 6,835 men killed in action, including 402 officers.
Ohioans first had military action at the Battle of Philippi Races in June 1861, where the 14th and 16th Ohio Infantry participated in the Union victory. Ohioans comprised one-fifth of the Union army at the April 1862 Battle of Shiloh, where 1,676 Buckeyes suffered casualties. Ohio would suffer its highest casualty count at the Battle of Chickamauga in September 1863, with 3,591 killed or wounded. Another 1,351 men were taken prisoner of war by the Confederates. Among these prisoners, 36 men from the 2nd Ohio Infantry would perish in the infamous Andersonville prison, as did hundreds more Buckeye soldiers there.
Several Buckeye regiments played critical roles in other important battles. The 8th OVI was instrumental in helping repulse Pickett's Charge at the Battle of Gettysburg. At the same battle, the 66th OVI flanked repeated Confederate assaults and helped secure the crest of Culp's Hill. George Nixon, great-grandfather of President Richard Nixon, died at Gettysburg in the 73rd OVI.
John Clem, celebrated as "Johnny Shiloh" and "The Drummer Boy of Chickamauga," became the youngest person to become a noncommissioned officer in United States Army history. More than 100 soldiers from Ohio units earned the Medal of Honor during the conflict. Several were awarded it for the ill-fated Great Locomotive Chase.
Dozens of small camps were established across the state to train and drill the new regiments. Two large military posts were created: Camp Chase in Columbus and Camp Dennison near Cincinnati. These later were used as prisons, but Johnson's Island, located in Sandusky Bay of Lake Erie is the most well known. Barracks and outbuildings were constructed for a prisoner of war depot, intended chiefly for officers. Over three years more than 15,000 Confederate men were held there. The island includes a Confederate cemetery where about 300 men were buried.
In September 1862, Confederate forces under Brig. Gen. Henry Heth marched through northern Kentucky and threatened Cincinnati (see Defense of Cincinnati). They turned away after encountering strong Union fortifications south of the Ohio River. Not long afterwards, Brig. Gen. Albert G. Jenkins briefly passed through the extreme southern tip of Ohio during a raid.
It was not until the summer of 1863 that Confederates arrived in force, when John Hunt Morgan's cavalry division traversed southern and eastern Ohio during Morgan's Raid. His activities culminated in Morgan's capture in Columbiana County. The Battle of Buffington Island was the largest fought in Ohio during the Civil War.