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The Commander of Fort Rosecrans Plans the Defense of San Diego in 1941, after the Attack on Pearl Harbor.
A methodically compiled map of coastal San Diego County from Solana Beach to the border with Mexico, stretching over twelve sheets and nine feet tall, substantially annotated in the immediate aftermath of Pearl Harbor as part of the organization of the defense of the city and its vital military bases against air—and sea-borne incursions by the Japanese. Based on internal and external evidence, the map appears to have been annotated by or for Colonel George Ruhlen (1884-1971), then commander of Fort Rosecrans on Point Loma in San Diego and one of those responsible for the city's defense.
The annotations reveal the earliest planning and considerations about the placement of searchlights (SL), observation posts (OP), and anti-aircraft and coastal artillery batteries. The annotations reveal primary and alternate placement considerations and viewshed sightlines that were almost certainly drawn on the spot.
This map had an interesting genesis and history prior to being pressed into service at the outset of American involvement in World War II. It was compiled in 1929 for Major General Ralph Henry Van Deman, who was then serving as commander of the 6th Infantry Brigade at Fort Rosecrans. Van Deman was a trained military cartographer and is sometimes called "the father of military intelligence" for his role in promoting the Military Intelligence Division (MID). He retired in September 1929 after nearly four decades of service, eventually settling in San Diego where he leveraged his old contacts from the WWI-era American Protective League (APL) into private counter-espionage consulting for the government. During WWII Van Deman worked with the War Department on integlligence matters.
The MID was responsible for "reproducing" this map according to imprints on the bottom-most sheets. Significantly, the MID was reorganized as the Military Intelligence Service in 1942. From this internal evidence, it is clear that this map was to be used as the basis for planning the defense of San Diego, as overseen by the commander of Fort Rosecrans.
Annotations
From north to south:
Torrey Pines Park:
"ALTERNATE SL [searchlight] / Position ALT 40' a fair Position" [with hatching indicating a blindspot at the base of the cliff]
"SL near Tea House / Torrey pines / a pretty good position"
"An excellent Position for an OP [observation post] / with a little cutting of trees" [Proposing cutting down now protected Torrey Pines to improve sightlines]
"300'" [in blue pencil]
La Jolla:
[Undefined emplacement symbol at Scripps Institute]
"SL Bird Rock Hill"
"OP Soledad Mt"
"Not very good for SL"
"ALT about / 35 ft"
"SL / La Jolla Hermosa / Point"
[Two triangular observation post symbols in red pencil on western points of Mount Soledad]
Crown Point:
AASL [anti-aircraft searchlight]
Ocean Beach and Point Loma:
[Unidentified emplacement symbol at the southern edge of the entrance to Mission Bay]
"ALT About / 45'" [with hatching to indicate blindspot at the bottom of Sunset Cliffs]
"A good position but a little low."
"Alternate / Position / too far back"
"SL Ocean Beach"
"a[lternat]e Position / [Oce]an beach"
[Street names in pencil at and around the Navy Training Sation Point Loma, i.e., Liberty Station]
Imperial Beach:
[Unidentified emplacement symbols at Coronado Heights]
"155 mm. Btry." [i.e., 155-millimeter artillery battery; see the below discussion of its move from Point Loma]
"A.A. Btry"
"SO. SAN DIEGO"
[Observation post triangle symbol in pencil and another in red pencil, somewhat higher up, at the highest point along the Mexican border near the water.]
The following is an excerpt from War Period History: Harbor Defenses of San Diego (Fort Guijarros Quarterly, Summer 1988, Vol. 1, No. 2, pp 19-22).
During the period of December 9 to 14, 1941, the 155 mm (G.P.F.) battery located in the northwest part of the [Fort Rosecrans] reservation was moved to Coronado Heights and named Battery Imperial. This relocation significantly extended the water area covered by the Harbor Defense guns to the south. All batteries eight inches and below were placed on constant anti-submarine alert status. Throughout the war, Harbor Defenses recorded sixty-one reports of enemy submarines, unidentified surface vessels, and underwater contacts off San Diego. Based on these reports, local defense ships and planes took action twenty-eight times during 1942 and 1943, and in 1943 alone, they dropped 115 depth charges. Despite these efforts, no friendly ships were sunk, nor were any enemy craft identified within the range of the Harbor Defense guns.
Before the war, all stations had either been base-end at Fort Rosecrans or across the channel entrance. New temporary base-end structures were established at La Jolla, Hermosa, above Ocean Beach, Coronado Heights, and at the Mexican border, ensuring complete coverage of the coastline and adjacent water areas within naval gun range of San Diego. Communications were extended to all these points from Fort Rosecrans.
One platoon of Battery "A" of the 19th Coast Artillery was sent to Camp Callan CARTC [La Jolla] to man 155 mm (G.P.F.) guns placed there. Although thousands of troops were at CARTC, the nature of their training did not make effective tactical manning of guns practical. This platoon remained in position for several months. Portable searchlights were also moved to provide illumination for all the new base-end stations.
Additionally, in the first week of the war, the Harbor Entrance Control Post was relocated to a room in the Harbor Defense Command Post structure. A fully integrated Joint Army-Navy command post was now established and continued to operate throughout the war.
Immediate action was taken to begin delayed construction on the Harbor Defense project and to approve and start work on the modernization program. Panama mounts were completed for Batteries Point Loma and Imperial in January 1942, enabling coverage of the entire coastline and adjacent water area from south of La Jolla to below the Mexican border by at least one battery of 155 mm (G.P.F.) guns.
Construction on new armament and base-end stations began immediately thereafter. Over the next two years, twenty-six new base-end stations and two new base-end command posts were completed. Portable searchlights were installed to serve these stations, and a total of twenty-two searchlights were in position at one time. New armament installations will be enumerated individually in order of completion. Additionally, a system of permanent buried Fire Control Communication cables was also started at this time. In a little over two years, the permanent cables were completed, significantly enhancing the communication capabilities of the Harbor Defenses. This infrastructure ensured efficient coordination and response times across all the newly established and existing base-end stations, effectively bolstering the overall defensive posture of San Diego's coastline and adjacent waters.
Rarity
The detailed annotations relating to coast defenses render the present map unique. We can not track another example of Van Demen's MID San Diego map in either OCLC or the relevant bibliographies.
Provenance
Colonel George Ruhlen (1884-1971); his personal map collection.
Colonel George Ruhlen (1884–1971) was a distinguished military officer and historical geographer whose career spanned significant developments in U.S. military history, particularly during the early and mid-20th century. Best known for organizing the coastal defenses of San Diego after Pearl Harbor, his leadership, particularly during World War II, and his contributions to historical scholarship made him a respected figure in both military and academic circles.
Born at Fort Totten, near Devil's Lake, North Dakota, in 1884, Ruhlen came from a family with a deep military tradition. His father, Major General George Ruhlen, was a U.S. Army quartermaster. Ruhlen graduated from the United States Military Academy at West Point and was commissioned as an officer in the U.S. Army. His early postings were within the Quartermaster Corps, but over time, he transitioned to roles of increasing responsibility within the field artillery, where he demonstrated keen leadership skills. His career saw him stationed at various posts, with a notable assignment in 1938 as the commanding officer of Corregidor, a fortress island in the Philippines critical to the defense of Manila Bay.
Colonel Ruhlen is perhaps best remembered for his role as the commander of Fort Rosecrans, a key military installation in San Diego, California. After the attack on Pearl Harbor on December 7, 1941, Ruhlen was tasked with organizing the coastal defenses of San Diego, a city that was seen as vulnerable to Japanese attack in the early days of the Pacific War. Fort Rosecrans, located on the Point Loma peninsula, became the centerpiece of Ruhlen’s efforts to fortify the region.
In his capacity as commander, Ruhlen oversaw the deployment of coastal artillery and anti-aircraft defenses, ensuring that San Diego, a vital Pacific Fleet base and a hub for wartime logistics, was well-protected. His leadership during this period was crucial in maintaining the security of one of the most strategically important cities on the U.S. West Coast.
Ruhlen retired from the U.S. Army in 1944, but his contributions to the San Diego community did not end there. He became heavily involved in historical research and preservation, notably serving as the president of the San Diego Historical Society during the late 1940s and early 1950s. In this role, Ruhlen was instrumental in promoting the study of Southern California's military history, especially the role that Fort Rosecrans and other installations played in the defense of the region during World War II.
Ruhlen’s work as a historical geographer extended beyond military history. He was particularly interested in the history of the American West and the strategic role of military forts in the development of the region. His research and writings contributed to a greater understanding of the military’s influence on the growth of Southern California, helping to preserve the legacy of the region's military past.
Colonel George Ruhlen was part of a family with a remarkable military lineage. His father, George Ruhlen Sr., served as an Army inspector general and was a significant figure in the U.S. Army during the early 20th century. Ruhlen's son, also named George Ruhlen, followed in his father’s and grandfather’s footsteps, serving with distinction in the U.S. Army during World War II. As a Lieutenant Colonel, George Ruhlen III commanded the 3rd Armored Field Artillery Battalion, a unit of the 9th Armored Division that played a key role in halting German advances during the Battle of the Bulge, particularly in the defense of Medernach.
