Fortress San Francisco

Giant Cannon Aimed at the Pacific

Townsley Gun No. 1 in 1942
Townsley Gun No. 1 in 1942


A historian once described San Francisco during World War II as “a giant cannon aimed at the Pacific,” - likening the millions of tons of cargo and munitions coming out of the port to projectiles sent against the Japanese military forces. During World War II, the U.S. Army and Navy arrayed a vast network of coastal fortifications, underwater minefields, antiaircraft guns, radars, searchlights, observation posts, and patrol aircraft, to protect the all-important entrance to the harbor, the Golden Gate and its famous bridge. Today, the still-impressive remains of that network can be seen at many locations in the Golden Gate National Recreation Area.

From as early as the California Gold Rush in the 1850s up through World War I, the U.S. Army had been continually constructing, expanding, and modernizing harbor defenses surrounding the Golden Gate, to keep enemies from capturing the port with its strategic military and industrial sites.  These new weapons and fortifications would form the backbone of San Francisco’s coastal defenses until after the end of World War II. 

Reluctantly Upgrading Defenses

Soldiers load Townsley No. 1 big gun
Soldiers load Townsley No. 1 big gun


As Europe headed deeper towards war in the 1930s, isolationist America reluctantly began to upgrade once again its coastal fortifications. In San Francisco, this program lead to the construction of two batteries, Battery Davis and Battery Townsley, the largest guns then in American arsenals. Each were 16-inch caliber rifled guns mounted on high elevation carriages, capable of firing 2,100 pound projectiles nearly 26 miles. On the eve of World War II, Battery Davis at Fort Funston and Battery Townsley at Fort Cronkhite formed the state-of-the-art defenses not only of San Francisco but also of the entire United States.

To protect the weapons against the growing threat of aerial bombardment, the army constructed each battery of two guns as a subterranean fortification with the guns aiming out from the sides of heavily camouflaged, manmade hills. Up to 20 feet of overhead concrete and earth cover provided protection for the guns themselves along with a labyrinth of connecting corridors, ammunition magazines, power plants, crew spaces, and assorted storage rooms. To protect the new batteries, the army placed antiaircraft guns nearby to ward off attacking enemy aircraft. (Even at this late date the army did not yet perceive the threat planes would pose to civilians. Instead, San Francisco’s prewar antiaircraft defenses were designed to protect military targets.)

Modern and Aging Batteries

On December 7, 1941, the Harbor Defenses of San Francisco Bay comprised a mixture of modern batteries as typified by Batteries Davis and Townsley; aging – but still potent – coast artillery emplacements constructed at the turn-of-the-century; mobile tractor drawn field artillery and antiaircraft guns; and the underwater minefields that still protected the shipping channels. Manning these defenses were an assemblage of “old army” regulars from the 6th Coast Artillery Regiment, newly-formed units such as the 18th, 54th and 56th Coast Artillery Regiments, and National Guard Regiments from as far away as Minnesota and Texas. When news reached San Francisco of the Japanese attack on Pearl Harbor, all off-duty personnel were recalled to their units and the harbor defenses put on full alert. Soldiers moved out of their barracks and into the batteries, and began filling sandbags, stringing barbed wire and constructing beach defenses at a fevered pace. Up and down the coast, observers in tiny concrete observation posts scanned the horizon for the approach of a Japanese fleet that would never come.

 The command center for all these activities was an underground facility covertly constructed at Fort Winfield Scott in the Presidio of San Francisco and dubbed the Harbor Defense Command Post/Harbor Entrance Command Post (HDCP/HECP). The crucial role of the HDCP/HECP was to defend the bay against enemy sea or air attack (the army’s role) and also to track and coordinate all shipping traffic in and out of the Golden Gate (the navy’s responsibility). 

As the days and weeks progressed, the initial fear of imminent invasion settled into a long-term commitment to defend the harbor by every means possible. Mobile antiaircraft guns, searchlights and radars were positioned on virtually every hill and knoll overlooking the Golden Gate. The U.S. Navy stretched an anti-submarine net across the inner harbor extending from the Marina in San Francisco to Sausalito in Marin, and stationed a navy tugboat to open and close the net to allow friendly shipping to pass. Soldiers assigned to the fortifications and observation stations constructed extensive earthwork trenches on the hillsides near their batteries, and in some cases tunneled into hillsides to construct unauthorized but comfortable underground quarters. Everywhere, camouflage paint was daubed on concrete batteries and wood barracks buildings, and acres of camouflage nets were stretched over fortifications to obscure their presence from highflying enemy planes. Overhead, navy blimps armed with depth charges patrolled offshore waters searching for Japanese submarines but only attacked the occasional unfortunate whale.

War's End and Beyond

Fortunately, no enemy ever attacked San Francisco, and by 1944 it was obvious to the army-navy commanders that invasion was a far distant likelihood. The soldiers of the harbor defenses were needed on battlefronts elsewhere, and starting that year the HDSF began to phase back its operations. With the signing of the peace treaty with Japan in 1945, the army reevaluated its need for fixed defenses, especially in the light of a new age of long-range bombers and nuclear weapons. The military phase out was speeded up, and by 1948 the last of the army’s San Francisco coast artillery fortifications had been scrapped.

Today, the remains of “Fortress San Francisco” can still be found throughout the Golden Gate National Recreation Area. In the Presidio of San Francisco, Battery Chamberlin at Baker Beach displays a rare 6-inch rifle on a 1903 disappearing carriage. Fort Point, a veteran of the Civil War, was pressed into use during World War II for a battery of 3-inch guns. Visitors can still explore the empty casemates of Batteries Davis and Townsley and at Rodeo Beach in Fort Cronkhite, visitors can experience the preserved 1940s “mobilization barracks” complex where the coast artillery soldiers lived. Across from Fort Cronkhite is Fort Barry, site of several 1900-era gun batteries that were armed during World War II. Many of these batteries still display remnants of their green-and-ochre camouflage schemes applied shortly after Pearl Harbor. Fort Barry managed Battery Wallace,  a 12-inch battery that was extensively rebuilt during World War II.  Observations posts, stretched along the San Francisco coastline from Point Reyes in the north to Half Moon Bay in the south, were tiny structures that housed a crew of observers who searched the horizon for the approach of enemy ships and, in the event of attack, direct the gunfire of the big guns through telephone communication. 

Last updated: December 3, 2015