The Seabees – “We Build, We Fight” in WWII

The full story of America’s combat construction force

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When the United States entered World War II after Pearl Harbor in 1941, the U.S. Navy suddenly faced a massive problem: it needed airfields, bases, fuel depots, docks, and roads built quickly across vast islands—many of them in active war zones. Ordinary civilian construction workers could not be sent into battle, and sailors weren’t trained to build major infrastructure. The solution was a completely new kind of military unit.

The Birth of the Seabees (1942)

Early 1942 U.S. Navy headquarters, Admiral Ben Moreell reviewing plans for the new Construction Battalions.

In early 1942, the Navy formed the Construction Battalions, soon nicknamed the “Seabees” from the initials C.B. The idea came from Rear Admiral Ben Moreell, who realized the Navy needed skilled workers who could also defend themselves.

Seabees were different from most military recruits. Many were older, highly experienced carpenters, electricians, miners, welders, heavy-machine operators, and engineers. These “builders in uniform” trained in both construction and combat. Their motto captured their role perfectly:

“We Build, We Fight.”

Training a New Type of Fighter-Builder

WWII-era Seabee recruits training on a beach, half practicing with rifles and half operating bulldozers and cranes.

Unlike traditional infantry, Seabees learned how to operate bulldozers, dynamite, cranes, and concrete mixers—right alongside learning how to handle rifles and defend construction sites. Their mission was not to seek battle, but they were fully prepared to protect themselves if needed.

Seabees in the Pacific: Building the Road to Victory

The Pacific Theater, filled with distant islands, became the Seabees’ main battleground. Their achievements were extraordinary:

1. Guadalcanal (1942–1943)

Seabees repairing Henderson Field under danger, bulldozers pushing earth, damaged airstrip.

At Guadalcanal, Seabees landed soon after Marines secured a beachhead. Under constant danger from enemy air attacks, they repaired and expanded Henderson Field, the airstrip that became the key to controlling the Solomon Islands. Their work enabled Allied aircraft to operate daily and helped turn the tide of the campaign.

2. The Island-Hopping Strategy

Seabees landing on a Pacific island with construction equipment loaded on landing craft.

Every new island required an instant transformation from jungle or coral into a functioning military base. Seabees built:

airfields for bombers and fighters
supply depots
oil storage tanks
docks and piers
roads and bridges
hospitals and camps

On islands like Tarawa, Makin, Kwajalein, Eniwetok, Saipan, Tinian, and Guam, Seabees often went ashore very early—sometimes while fighting was still dangerously close—to start construction.

3. Tinian: The Most Important Runways of the War

Wide aerial-style view of Seabees constructing giant runways on Tinian, rows of heavy machinery carving straight airstrips.

On the island of Tinian, Seabees built what became the largest airbase in the world at the time. They carved out massive airstrips capable of supporting B-29 bombers. From these runways, the U.S. launched long-range missions over Japan—including the atomic bomb missions (the Seabees’ role was construction only; they were not involved in mission planning).

4. Iwo Jima (1945)

Seabees building an airfield on Iwo Jima’s black volcanic sand, Marine patrols nearby, bulldozers pushing ash and gravel.

At Iwo Jima, Seabees worked almost immediately after Marines secured small sections of beach. The island’s volcanic sand made construction extremely difficult, but they quickly built airstrips that served a crucial role: thousands of damaged B-29 bombers used them as emergency landing fields on their way back from Japan.

Seabees in Europe and Africa

Most Seabee action is remembered in the Pacific, but they also played a major part elsewhere:

North Africa (1942–1943)

Seabees repaired and expanded ports to support Allied armies moving toward Tunisia.

Sicily and Italy (1943–1945)

They cleared rubble, restored ports, and built facilities that kept supplies flowing as Allied forces advanced up the Italian peninsula.

D-Day and Western Europe (1944–1945)

Seabees working on floating pontoons for the Mulberry harbors after D-Day, rough seas, cranes assembling massive steel structures.

Seabees helped construct and operate the Mulberry harbors, the artificial floating ports that allowed Allied supplies to come ashore in France after D-Day. Their engineering skill helped make the invasion sustainable.

The “Lion,” “Cub,” and “Acorn” Bases

To support the Navy across the globe, the Seabees helped create standardized base packages like:

Lion bases – full-scale naval bases
Cub bases – medium-sized bases
Acorn units – specialized airfield construction teams

These standardized kits let the Navy build bases quickly, almost like assembling enormous military “legos.”

Innovations and Ingenuity

One of the Seabees’ defining qualities was creativity under pressure. They often invented solutions on the spot:

modifying bulldozers to push through jungle under fire
building pontoon causeways to unload supplies on beaches
salvaging wrecked materials for rapid repairs
constructing roads through swampy or volcanic terrain

In the Pacific, they even built entire artificial islands and harbors using giant steel pontoons.

Life as a Seabee

Daily life was demanding. Seabees worked long hours in extreme heat and humidity, often with little rest. They lived in rough camps, faced attacks from the air, and navigated difficult terrain. But their spirit—often captured through songs, cartoons, and mascots—remained strong. Their unofficial symbol, the “Fighting Bee,” carried a wrench, hammer, and machine gun.

War’s End and Legacy

Post-WWII Seabee group portrait at a Pacific base, holding tools and unit flags, bulldozers in background.

By the end of WWII:

over 325,000 men had served as Seabees
they built over 400 advanced bases
they completed more than 300 major airstrips
their work spanned 300+ islands and every major theater

The Seabees became legendary for reliability, toughness, and engineering skill. After WWII, the Seabees continued serving in Korea, Vietnam, the Cold War, natural disaster relief missions, and modern humanitarian operations.

Why the Seabees Mattered

Their contribution was absolutely essential to Allied victory. Battles could not be fought—let alone won—without the runways, harbors, and supply bases the Seabees built. They proved that construction and engineering could be just as important as traditional combat.

The motto “We Build, We Fight” remains the perfect summary of a force that used bulldozers and determination to help win World War II.