At the outbreak of war with Spain in 1898, the U.S. Army was very small in numbers. This situation necessitated an immediate call for volunteers. President McKinley’s appeal was overwhelmingly answered by a generation that had grown up in the shadow of their elders’ Civil War glory. One group answering the call was the First Regiment of the U.S. Cavalry Volunteers, headed by Colonel Leonard Wood, a distinguished army doctor and Medal of Honor recipient. The regiment was actually the brainchild of Theodore Roosevelt, assistant secretary of the navy and Wood's friend. Roosevelt, realizing his own lack of military experience, suggested Wood for the command. The Rough Riders, as the regiment was soon known, comprised 1,250 men, including cowboys, Indians, and eastern college athletes. Despite their dissimilarities, they were in excellent physical condition—a stark contrast to most of the other volunteer contingents. The Rough Riders departed from Tampa in mid-June without their horses. They landed at Daiquiri on June 22 and two days later served with distinction in a battle at Las Guásimas. Immediately prior to the conflict at San Juan, Colonel Wood was promoted to another field command, enabling Teddy Roosevelt as a full colonel to take command of the Rough Riders. On July 1, Roosevelt, having secured a horse, led his forces in a charge up Kettle Hill outside of Santiago. They achieved their goal and later in the day participated in the victory at San Juan Hill. By seizing these heights, American guns commanded the harbor at Santiago. The Spanish position was imperiled and an abortive attempt by the Spanish navy to escape from the harbor was halted with devastating results. Spanish land forces surrendered shortly thereafter. Theodore Roosevelt urged the Rough Riders' swift evacuation, fearing the continuing spread of disease. They returned to Montauk, Long Island, where they were held in quarantine before being mustered out in September. More than one-third of the Rough Riders were casualties in the Spanish-American War, a fact that has led some observers to criticize Roosevelt for unnecessary risk-taking. Nevertheless, the Rough Riders became heroes to the American public and Theodore Roosevelt emerged as a major national figure.