On 25 April 1898, the United States declared war on Spain, beginning the Spanish–American War. The 8th Ohio Volunteer Infantry was mustered into service on 13 May 1898 in Columbus, Ohio, and had 48 officers and 838 enlisted men on its roster. They arrived at Camp Alger, Virginia on 20 May, and trained there until 5 July, when they received orders to deploy to Santiago, Cuba under the command of GEN Nelson A. Miles. The regiment arrived in Siboney, Cuba on 10 July and reinforced the V Army Corps under GEN William Rufus Shafter. 0600 on 11 July, the American lines were ordered to open fire on the Spanish defenses. The barrage was very effective and much damage was done to the defending force. The batteries opened upon the enemy from El Pozo Hill, and the American fleet fired its shells into the city of Santiago. Every preparation had been made for a combined assault both by land and sea. Spanish General Toral had twice refused to make an unconditional surrender, and GEN Shafter, Commodore Winfield Scott Schley and Commodore William T. Sampson determined to give the Spaniards only one more chance and then destroy the city of Santiago with the batteries from the shore and on the war-ships. As the day progressed, the firing became heavier. From the sea, the bombardment was begun by the USS "Newark" with its 8-inch guns, and then the USS "New York" and USS "Brooklyn" followed. The men of the 8th Ohio could see the men of the Signal Corps on a high ridge wigwagging to direct the shots to the ships. The first heavy volley fired from the American lines almost effectually silenced the Spanish soldiers in the trenches, and hardly a sign of life could be seen there. The Siege of Santiago ended shortly after, on 17 July 1898, and the remained on occupation duty in Cuba until 18 August. They returned to the US on 26 August, and mustered out of service on 21 November 1898. In Cuba, the 8th Ohio lost 4 officers and 68 enlisted men due to Yellow fever.