Fort Miles’ $22 Million Defense of Delaware Bay
When Nazi U-boats sank 300 ships off the East Coast in 1942, Fort Miles stood ready.
Built at Cape Henlopen to guard vital shipping lanes to Philadelphia, this massive fort cost $22 million and housed 2,500 troops. Construction began in March 1941, then sped up after Pearl Harbor.
The fort packed serious punch—from 3-inch anti-aircraft guns to massive 16-inch naval cannons—plus coastal towers to spot enemies.
Though its guns never fired in battle, Fort Miles later claimed a victory when German submarine U-858 surrendered there in May 1945.
Today, Cape Henlopen State Park preserves this coastal defender where you can explore Battery 519’s underground museum.
The Nazis Forced America to Beef Up Its Coastal Defenses
German tanks rolled across Western Europe in 1940, setting off alarms for U. S. military planners. The Army quickly saw that Delaware Bay needed protection since it led straight to the Philadelphia Naval Shipyard and major oil refineries.
The Harbor Defense Board got to work, calling for 27 huge gun batteries across the country. Army engineers showed up at Cape Henlopen that summer with measuring tools.
They knew the Delaware River would be a prime target if Hitler ever sent his navy across the Atlantic.
Construction Crews Raced to Build a Fortress by the Sea
Workers started digging at Cape Henlopen on March 24, 1941, beginning with Battery Smith for the planned 16-inch guns.
The first weapons arrived just weeks later – four mobile 155mm guns brought by the 21st Coast Artillery Regiment. Delaware National Guard soldiers from the 261st Coast Artillery Battalion came on June 5.
The Army called the growing base “Fort Miles” on June 3 after Civil War hero Lieutenant General Nelson A. Miles.
By June 1942, crews finished concrete stands to hold the mobile guns steady during firing.
Pearl Harbor Turned Construction Into a Round-the-Clock Job
The Japanese attack on December 7, 1941, lit a fire under everyone at Fort Miles. Construction sped up as workers rushed to finish more gun batteries.
Plans grew to include Battery 519 with 12-inch guns and Batteries Herring and Hunter with 6-inch guns. The Army Corps of Engineers brought in hundreds more workers.
Crews dug deep underground bunkers and built tall fire control towers along the coastline. Teams also began laying underwater mines across Delaware Bay to Cape May to block enemy ships.
A Small City Sprang Up Behind the Dunes
Fort Miles grew into a busy military community with nearly 2,500 soldiers and civilian workers by 1942. The base spread across more than 1,000 acres with over 250 buildings.
It cost $22 million, worth about $420 million today. Barracks, mess halls, offices, and recreation buildings popped up among the sand dunes.
Workers built 11 concrete fire control towers along the coast to spot and track enemy ships. The towers still stand today, watching over the beaches.
Big Guns Stood Ready to Blast Enemy Ships
The fort bristled with firepower, from massive 16-inch naval guns to smaller 3-inch anti-aircraft weapons. Battery Smith had two 16-inch guns that could throw 2,240-pound shells more than 25 miles.
The fire control system connected observation towers with underground command centers for precise targeting. Workers covered all gun batteries with sand and camouflage to hide them from enemy planes.
Fort Miles became the main defense guarding Delaware Bay, ready to stop any German warships that might threaten Philadelphia.
German U-Boats Brought War to American Shores
German submarines started Operation Drumbeat in January 1942, bringing the war right to America’s doorstep. U-boats sank over 300 Allied ships in the first six months, killing more than 6,000 sailors.
Enemy submarines often lurked within sight of the coast, sometimes in water shallow enough to see the bottom. Fort Miles kept constant watch, but German captains wisely stayed underwater, avoiding the fort’s big guns.
Many coastal towns kept their lights on at night, making ships perfect targets against the glowing shoreline.
The Fort’s Guns Never Fired a Shot in Anger
Despite years of readiness, Fort Miles never fired its guns in actual combat. Soldiers ran regular training exercises and target practice to stay sharp.
The fort scored high marks during shooting tests and military inspections. The German surface fleet that planners feared never showed up in Delaware Bay.
Hitler’s navy focused on submarine warfare instead of sending battleships across the Atlantic. The fort’s gunners waited for an enemy that never came.
A German Sub Crew Surrendered Just Off the Beach
German submarine U-858 gave up on May 10, 1945, just days after Hitler’s defeat. The USS Pillsbury and USS Pope brought the captured U-boat to Cape Henlopen on May 14.
Fort Miles took in 37 German sailors, making this the first enemy surrender to American forces since the War of 1812. Guards held the submariners briefly before sending them to POW camps farther inland.
The U-858 never sank any Allied ships during its short combat career.
The Army Moved Out as the Cold War Heated Up
The Army called most of Fort Miles surplus property by 1949.
The Navy quickly claimed sections for Cold War operations, including Operation Bumblebee missile testing.
Johns Hopkins Applied Physics Lab used the beaches for rocket tests from 1945 to 1947, shooting experimental missiles over the Atlantic.
In 1960, the Navy set up NAVFAC Lewes as part of the SOSUS submarine detection network. The old battery buildings found new life as offices, storage spaces, and homes for communications equipment.
Secret Submarine Hunters Worked Underground
NAVFAC Lewes ran from 1960 to 1981 as a secret submarine detection facility.
The Navy turned Battery Herring into a high-tech sonar processing center filled with computers and listening equipment. Navy personnel watched Soviet submarine movements in the Atlantic around the clock.
The operation stayed secret until the government revealed the SOSUS program in 1991.
The Biden Environmental Center later took over buildings originally built as Navy headquarters and housing for the listening post staff.
The Fort Now Teaches Visitors About Coastal Defense
Delaware received 554 acres of Fort Miles in 1964, creating Cape Henlopen State Park. The Fort Miles Historical Association formed in 2003 to save and share the base’s military history.
Battery 519 transformed into the Fort Miles Museum, showing how coastal defenses worked and how soldiers lived.
In 2016, the museum installed an original 16-inch gun from the battleship USS Missouri as its centerpiece display.
Today, Fort Miles helps visitors understand how America protected its shores during World War II, preserving a crucial chapter in our national defense story.
Visiting Cape Henlopen State Park, Delaware
Cape Henlopen State Park at 15099 Cape Henlopen Drive in Lewes preserves Fort Miles, a $22 million World War II installation that housed 2,500 soldiers protecting Delaware Bay from German attacks.
Entry costs $5 for Delaware residents and $10 for out-of-state visitors March through November.
You can explore Battery 519 Museum, climb Fire Control Tower #7 for coastal views, and see the free Oil Still Bleeds exhibit. Behind-the-scenes guided tours cost extra.
This article was created with AI assistance and human editing.
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