Camp Callan was established in 1941 on the Torrey Pines mesa in response to the sudden expansion demands of a nation moving toward war. The site was chosen for its geography: the flat tabletop of the mesa provided space for barracks and training ranges, while the proximity to the coast made it appropriate for anti-aircraft training — the guns could be aimed at towed target sleeves over open water without the complications of urban proximity. The camp covered roughly 2,000 acres and at its peak housed thousands of trainees simultaneously. It was named for Robert Callan, a California-born general who had served in the Philippines and the Spanish-American War. During the war years, the mesa that now feels like a quiet suburban district was a military installation operating at full capacity.

Anti-aircraft artillery training was technical work. Soldiers had to learn not just to operate heavy guns but to track moving targets — aircraft traveling at speeds and altitudes that required calculating where a shell would be by the time it arrived, not where the plane was when it fired. The training at Camp Callan incorporated towed sleeve targets, searchlight operation, and the fire-control instruments required to coordinate battery fire. Trainees rotated through in thirteen-week cycles, which meant the camp processed roughly 15,000 men per year. Many of the soldiers who trained at Camp Callan went on to serve in Pacific island campaigns where Japanese air attacks were an operational reality. The training was designed for exactly those conditions.

Camp Callan closed in 1945, shortly after the end of the war. Unlike some military installations that were repurposed intact, the camp was largely demolished — its buildings were temporary structures intended for wartime use, not permanent facilities. The land became surplus federal property and was eventually transferred for civilian use. The Torrey Pines Municipal Golf Course opened on the northern portion of the former camp grounds in 1957; it would later achieve international recognition as the host of the 2008 U.S. Open. The University of California San Diego, established in 1960, occupies the southern and eastern portions of what had been camp territory. The mesa that trained anti-aircraft gunners is now home to one of the country's leading research universities.

The physical traces of Camp Callan are essentially gone. No barracks survive. No gun emplacements mark the bluff edges. The Torrey pines that give the area its name — a rare pine species found naturally only here and on Santa Rosa Island, a population that survived both the Spanish land grants and the wartime occupation — continue their slow growth on the coastal slopes below the mesa. The golf course fairways, which drop dramatically toward the ocean on the western edge of the mesa, follow roughly the same topography that once defined the camp's coastal boundary. Players standing on those fairways have the same view of the Pacific that anti-aircraft gunners once scanned for incoming aircraft. The vista is unchanged. The reason for watching it has not been the same for eighty years.