On July 1, a combined force of about 15,000 American troops in regular infantry and cavalry regiments, including all four of the army's "Colored" Buffalo Soldier regiments, and volunteer regiments, among them Roosevelt and his "Rough Riders", the 71st New York, the 2nd Massachusetts Infantry, and 1st North Carolina, and rebel Cuban forces attacked 1,270 entrenched Spaniards in dangerous Civil War-style frontal assaults at the Battle of El Caney and Battle of San Juan Hill outside of Santiago. More than 200 U.S. soldiers were killed and close to 1,200 wounded in the fighting, thanks to the high rate of fire the Spanish put down range at the Americans. Supporting fire by Gatling guns was critical to the success of the assault. Cervera decided to escape Santiago two days later. First Lieutenant John J. Pershing, nicknamed "Black Jack", oversaw the 10th Cavalry Unit during the war. Pershing and his unit fought in the Battle of San Juan Hill. Pershing was cited for his gallantry during the battle. The Spanish forces at Guantánamo were so isolated by Marines and Cuban forces that they did not know that Santiago was under siege, and their forces in the northern part of the province could not break through Cuban lines. This was not true of the Escario relief column from Manzanillo, which fought its way past determined Cuban resistance but arrived too late to participate in the siege. After the battles of San Juan Hill and El Caney, the American advance halted. Spanish troops successfully defended Fort Canosa, allowing them to stabilize their line and bar the entry to Santiago. The Americans and Cubans forcibly began a bloody, strangling siege of the city. During the nights, Cuban troops dug successive series of "trenches" (raised parapets), toward the Spanish positions. Once completed, these parapets were occupied by U.S. soldiers and a new set of excavations went forward. American troops, while suffering daily losses from Spanish fire, suffered far more casualties from heat exhaustion and mosquito-borne disease. At the western approaches to the city, Cuban general Calixto Garcia began to encroach on the city, causing much panic and fear of reprisals among the Spanish forces. Battle of Tayacoba Lieutenant Carter P. Johnson of the Buffalo Soldiers' 10th Cavalry, with experience in special operations roles as head of the 10th Cavalry's attached Apache scouts in the Apache Wars, chose 50 soldiers from the regiment to lead a deployment