Fort Huachuca's first decade defined its character. The installation controlled access to the Mexican border and the mountain passes that Apache bands used for raids and retreats. In 1886, General Nelson A. Miles made the fort his headquarters for the final campaign against Geronimo, the Chiricahua leader who had eluded capture for years. That September, Geronimo surrendered, ending the Apache Wars and the last major military conflict against Native Americans. The fort should have closed. Most frontier posts did once their reason for existence vanished. But Huachuca's strategic position near Mexico kept it relevant, a buffer zone that would prove useful in ways no one anticipated.

In 1913, the 10th Cavalry Regiment rode through Fort Huachuca's gates and stayed for twenty years. These were the Buffalo Soldiers, African American cavalrymen whose nickname came from Plains Indians who compared their curly hair to buffalo pelts. At Huachuca, they found something rare in the segregated Army: a post where they were the main force, not an afterthought. During General John J. Pershing's Punitive Expedition into Mexico in 1916-1917, chasing the revolutionary Pancho Villa, Fort Huachuca served as a forward logistics base. From 1916 to 1917, Colonel Charles Young commanded the post, becoming the first African American to reach that rank. The fort declared its Buffalo Soldier heritage a National Historic Landmark in 1976.

World War II transformed Fort Huachuca from a cavalry post into a small city. At its peak, the installation housed quarters for 1,251 officers and 24,437 enlisted soldiers. The 92nd and 93rd Infantry Divisions, both composed of African American troops, trained here before deploying to combat theaters. Hundreds of Women's Army Corps members served on post. When the war ended, the Army closed the fort in 1947 and handed it to the Arizona Game and Fish Department. Buffalo roamed the former parade grounds. But the Korean War brought the military back, and engineers built Libby Army Airfield, named for Medal of Honor recipient George D. Libby. The fort has stayed open ever since.

The post-Korean War era gave Fort Huachuca a new mission: electronic warfare. The Army's Electronic Proving Ground opened in 1954, testing everything from radios to radar systems. The Army Security Agency established a test center in 1960. The Electronic Warfare School followed in 1966, the same year the Vietnam War drove massive demand for communications specialists. By 1967, Fort Huachuca had become headquarters for the U.S. Army Strategic Communications Command. Today it hosts NETCOM, the Army Network Enterprise Technology Command, responsible for cyberspace operations across the service. A tethered radar balloon floats above Garden Canyon, scanning for drug traffickers' aircraft crossing from Mexico.

Fort Huachuca is the center of Army military intelligence training. The 111th Military Intelligence Brigade teaches officer and warrant officer courses in human intelligence, imagery analysis, and electronic surveillance. The U.S. Army Intelligence Museum displays artifacts from a century of espionage, including an Enigma Code machine and a section of the Berlin Wall. Until 2006, the Army's drone program was headquartered here. Over 18,000 people work on post during weekday hours, a mix of 6,500 active duty soldiers, 7,400 family members, and 5,000 civilian employees. The runway at Libby Army Airfield, shared with Sierra Vista Municipal Airport, was once designated as an emergency landing site for the Space Shuttle, though it was never needed.