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.