"Hello Tojo" is the friendly greeting on this replica of a 1-ton big gun shell.

Battery Townsley

Mill Valley, California

The United States flaunts its 12,000+ mile coastline -- desirable beachfront property that can't help but entice foreign enemies. Coastal military fortifications at key cities and harbors, erected since the nation's earliest days, have evolved as new threats emerged. Defense for San Francisco Bay, which began with cannons in stone forts, prepped for potential coastal hostilities right up until the 1970s.

U.S. Navy Mark VII #386.

A restoration of historic Battery Townsley, in the Golden Gate National Recreation Area, provides a vivid walk-through view of life in a World War 2-era artillery bunker. And it also provides the "good" Terminator with a hidey-hole to await the next battle for the future of mankind.

Perched in the Marin Headlands north of San Francisco, Battery Townsley offers a spectacular view of the Pacific Ocean. The vantage point was ideal for sending a welcome message of one-ton, armor-piercing shells to any enemy fleet appearing on the horizon. Today, the old military site is accessible by a strenuous, 3/4 mile walk to a hilltop. On a weekend, relentless waves of hikers, dog walkers, and cyclists make the climb. Battery Townsley offers monthly open house tours conducted by knowledgeable volunteers. Guide Fred Schwartz led us into the cool interior of the bunker, and fellow volunteer Greg Jennings provided other historical details.

Battery Townsley, overlooking the Pacific Ocean.

After World War I, when aerial bombing became a viable threat, America's most likely west coast aggressor was a newly-militarized Japan and its Imperial Navy. Seacoast defenses had to change. Planning for the 2-gun battery named after Major General Clarence P. Townsley, part of Fort Cronkhite, started in 1928, a camouflaged catacomb of 26 rooms under concrete up to 14 ft. thick.

Prop hatch from the film "Terminator Genisys."

U.S. Navy Mark II/III guns were used by the U.S. Army Coast Artillery Corps, originally manufactured decades earlier for two classes of planned battleships cancelled by the Washington Naval Treaty of 1923. A later screwup in battleship design rendered those guns too heavy to install on ships. As a testament to creative redeployment, a bunch of 143-ton guns were moved out of storage to beef up America's coast artillery defenses. In the late 1930s, the Army Corps of Engineers dug Five Minute Tunnel, one of two ways to enter Fort Cronkhite, to allow the guns to be delivered. They carved a concrete, single lane road up to the battery, which became active in 1940.

Two gun batteries were "casemated" under protective concrete walls and roofs, and camouflaged to avoid detection. The location of Battery Townsley, along with other coastal fortifications on military property, was top secret. The perimeter was crisscrossed with barbed wire and pillboxes, and patrolled by guards. There's a surviving machine gun nest, still visible with sandbags in place, on the hill above Townsley, along with a bomb shelter tunnel from the Korean War.

Nuclear-explosion pressure simulation tube.

Townsley's giant guns, cranked to a 65 degree angle, could lob a 2,100 lb. armor-piercing shell 25 miles, the same range as the newest battleships at the time. The facility bustled with over 100 soldiers. A chalkboard listing duty assignments includes Gun Pointer No. 1 and No. 2, Range Setter, Air Pressure Operator, Chief of Ammunition, and 35 Cannoneers.

Battery Townsley was staffed around the clock. They had to be ready to fire on five minutes notice...and continue firing every 90 seconds.

On first use, the crew discovered that all the facility doors would have to be opened before the gun was fired. The inaugural blast's back pressure blew servicemen up the corridor, ripping open pants and jacket seams.

Battery Townsley was vigilant and ready for several years, but halfway through World War 2 American military leaders realized that the weakened Japanese Imperial Navy was unlikely to threaten the Pacific coast. At the end of the war in 1945, Battery Townsley had not fired a shell at an enemy.

The big guns were removed and scrapped in 1948. For the next twenty years, the repurposed site provided quarters for Nike missile crews and served other Cold War functions. The underground bunker received a new mission from 1965-1974. One of the corridors was outfitted with a tube for scientists and engineers to conduct force tests on materials and objects with nuclear-explosion simulating pressures. Someone must have recalled all those cannoneers tumbling up the corridor. Visitors can peer up the nuclear simulation tube during the tour.

The military finally decommissioned the site in 1974. It quickly became an untended urban exploration ruin and local drinking hangout. The concrete surfaces were covered with graffiti. Chuck Wofford, a preservationist who saw its potential for educating visitors to Golden Gate National Recreation Area, left a $230k bequest specifically to restore Townsley. It opened for tours in 2007.

In 2014, Battery Townsley was the filming site for scenes in the sci-fi movie Terminator Genisys, the fifth movie in the franchise, and starring post-governor Arnold Schwarzenegger. In the movie script it's an abandoned bunker in the Marin Headlands, used by a "good" Terminator as a kind of Fortress of Solitude while he awaits the arrival of time travelers.

One key fixture in the film's bunker scenes was a large circular metal hatch to Arnold's lair (So heavy! That Terminator, so strong -- we are grateful he's on our side.). The prop hatch leans against a wall deep inside Battery Townsley. At the entrance, volunteers usually have a binder of photos on hand from the movie shoot, along with more legitimately historical photos and maps.

Though the original big guns were scrapped, Townsley exhibits a big gun that actually engaged with the enemy.

U.S. Navy Mark VII #386 was originally mounted on the Battleship Missouri, used in World War II. It witnessed the Japanese surrender on September 2, 1945, and served in the Korean War. Eventually the gun was retired and stored at the U.S. Navy Weapons Station in Hawthorne, Nevada. The Navy was planning to chop up their pile of battleship guns, but was persuaded to save one for Townsley. It was the same length (68-ft.) and caliber as the guns that had been at Fort Cronkhite, so the relic was resurrected, shipped and installed for display in 2012.