At the outbreak of the Spanish–American War in April 1898, "Indiana" was at Key West with the rest of the North Atlantic Squadron, at the time commanded by Rear Admiral William T. Sampson. His squadron was ordered to the Spanish port of San Juan in an attempt to intercept and destroy Admiral Cervera's Spanish squadron, which was en route to the Caribbean from Spain. The harbor was empty, but "Indiana" and the rest of the squadron bombarded it for two hours on 12 May 1898 before realizing their mistake. The squadron returned to Key West, where news arrived three weeks later that Commodore Schley's Flying Squadron had found Cervera and was now blockading him in the port of Santiago de Cuba. Sampson reinforced Schley on 1 June and assumed overall command.