During World War II, “island hopping” was key to Allied victory in the Pacific theatre. This allowed Allied forces to bypass heavily fortified Japanese-occupied islands and instead capture more lightly defended locations that could support the next military advance. A cornerstone of the island-hopping strategy was the Naval Construction Force—more commonly known as the Seabees—which would convert these sparsely occupied atolls and islands into formidable naval bases and airfields. These advance bases, such as Espiritu Santo (resupply and ship repair), Tinian (launch point for the mainland Japan strategic bombing campaign), and Saipan (seaplane base, hospital) were the logistics backbone of the Pacific war.1
In addition to their history of building critical infrastructure for naval campaigns, the Seabees have a unique relationship with the Marine Corps. When the Seabee battalions were first formed, initial military training was conducted by a Marine cadre, and unit organization mirrored the Marine Corps structure—using squads, platoons, companies, battalions, and regiments instead of work centers, divisions, and departments as seen in the Navy.
The bond between the Seabees and the Marine Corps extended deeper than training and organization when the 133rd Naval Construction Battalion joined the 4th Marine Division in the initial amphibious assault on Iwo Jima, during which the Seabees suffered 328 casualties, including 42 killed in action.2 This bond continued throughout the Korean and Vietnam Wars, in which Seabees deployed and bled alongside Marines. Today, a Seabee task force doctrinally forms the naval construction element of the Marine air-ground task force. This was demonstrated during Operation Enduring Freedom, when the 25th Naval Construction Regiment and subordinate battalions built and maintained the Marine Corps’ main operating base, Camp Leatherneck, and other combat outposts for the duration of their involvement in Afghanistan.3 With the Navy’s focus on competing with China and the Marine Corps’ Pacific focus in Force Design 2030, the Seabees are returning to their Pacific island-hopping roots.
Naval Mobile Construction Battalion: Core of the Naval Construction Force
Discussions among Seabees, old and young, usually start: “Who did you serve with?”—meaning “In which naval mobile construction battalion (NMCB) did you spend most of your career?” Most Seabees join one of six active (three in Port Hueneme, California, and three in Gulfport, Mississippi) or five reserve NMCBs early in their careers. They learn the basic tactical, technical, and planning skills to earn their primary warfare device, the Seabee Combat Warfare pin—more commonly known as the “bug.”
While NMCBs train to build and fight as a cohesive single formation, they also train and deploy in company-size and airlift-capable “air detachments” or smaller platoon-sized detachments. There is no overarching equipment list for these flexible engineering detachments. Chiefs and officers are trained to quickly mission plan and build task-tailored teams of personnel and equipment, sourced from the parent NMCB, to accomplish a variety of engineering tasks. The primary strength of an NMCB is flexibility, as battalions regularly deploy more than ten detachments to different continents and countries as part of peacetime and combat deployments.
The Naval Construction Force is adapting to support the Navy’s focus on China and the Marine Corps’ Force Design 2030. Since 2019, each NMCB has tailored the advanced and integrated phases of its fleet readiness training plan cycle to practice and test operational concepts that deploy the battalion’s engineering capabilities to remote islands.4 These efforts culminated in February 2023 when Director, Expeditionary Warfare, published OpNavInst 3501.115G: “Required Operational Capabilities and Projected Operational Environment for the Naval Construction Force,” outlining how the Naval Construction Force and NMCBs will reorganize and adapt to the maritime battlespace.5
Previously, an NMCB certified as a battalion and companies were organized by ratings and general technical roles. When given a specific task, a battalion was expected to build ad hoc detachments drawn from multiple companies to accomplish the mission. However, OpNavInst 3501.115G instructs battalions to reorganize to support specific fleet objectives by maintaining permanent certified deployable companies around specific missions, such as airfield construction, waterfront construction, and advanced base construction, with some trained to build and operate 150-bed expeditionary medical facilities. The NMCB headquarters element would serve as an O-5–level battle staff that exercises command and control over other Naval Construction Force and joint force engineering units. The NMCBs will be tasked to repair and construct the most forward positioned vital infrastructure where Navy and Marine Corps units are based in competition and conflict.
Furthermore, while all active and reserve battalions today are organized as NMCBs, the Naval Construction Force’s new required operational abilities/projected operational environment instructions call for reorganizing the Reserve NMCBs into naval construction battalions. Active-duty NMCBs focus on expeditionary airfield, waterfront, and advanced base construction while being capable of intratheater movement via aircraft and amphibious vessels. Reserve naval construction battalions will include companies primarily focused on mineral production (producing aggregates for road, port, and airfield construction because they are not available on Pacific Islands), road construction, and general construction, including forward operating bases and intermediate staging bases. These naval construction battalions are designed to focus on the large land-based engineering projects to build out advanced naval bases and intermediate staging bases that support intense naval operations.
The Underwater Construction Team: Unique, Mission Critical Specialists
Seabee divers started as small attachments to battalions conducting waterfront construction or dredging operations during World War II. Interestingly, naval combat demolition units, the predecessors to Navy SEALs, originally were trained as Seabee divers and performed amphibious demolition and combat engineer tasks. After World War II, units conducting demolition and amphibious combat engineering missions formed independent underwater demolition teams, which grew into today’s Naval Special Warfare community.
Divers remained attached to NMCBs until the two contemporary underwater construction teams (UCTs) were formed as independent commands in 1974 because of a growing need for trained divers who could build and repair underwater structures. For the first few decades of their existence, Seabee divers focused on waterfront construction on far-flung naval installations across the globe. Emblematic of the early UCTs and they work they did is Petty Officer Second Class Robert Stethem (namesake of the USS Stethem [DDG-63]), who was killed during a Hezbollah hijacking while returning from a waterfront construction mission in Souda Bay, Crete, in 1985.6
UCTs have received renewed attention and focus as the Naval Construction Force shifted its focus from supporting operations in the Middle East to competing with China in the western Pacific. Each UCT is growing from approximately 75 Seabees, organized around three 12-person deployable construction dive detachments and a nondeployable headquarters element, to more than 200 built around four 18-person dive detachments and an O-5–level battle staff and headquarters element capable of conducting command and control over other Naval Construction Force and joint force engineering units. There are even plans to stand up a third UCT or add more dive detachments to each UCT, contingent on growing the Seabee dive school pipeline. Because a potential kinetic conflict in the Pacific would involve building additional and redundant naval bases with ports and anchorages, UCTs’ mission is a fleet necessity.
Seabees in Action: Cooperation, Competition, and Conflict
The Seabee motto, “We Build, We Fight,” implies that their primary role exists within the kinetic phase of military operations. However, Seabees also deploy extensively in support of peacetime fleet objectives.
Cooperation
While Seabees are trained in both tactical and technical skills, their construction skills make them ideal for building persistent international partnerships and cooperation. Seabee battalions deploy and sustain detachments on small Pacific-island nations such as Palau and Micronesia, where they maintain an enduring presence. In most cases, Seabees stay for three to five years. In the case of Civic Action Team (CAT) Palau, Seabees have had a continuous presence for more than 50 years.7
Detachments work closely with U.S. embassies to positively shape the population’s opinion of the United States. While China has used its large-scale loan-based Belt and Road Initiative and casino-centric tourism to direct investment and influence in these Pacific island nations, the Seabees have driven grant-based infrastructure projects that are smaller but invested directly in the community. While the rest of the Navy and Marine Corps primarily build military-to-military relationships during joint exercises, Seabees are on the ground for years, interacting with local people, governments, and militaries, and proving that the U.S. Navy cares and is a force for good.
Competition
In the more overt competition phase of military operations, Seabees also contribute significantly by building physical infrastructure that enables fleet maneuver and building up partner-nation naval forces. For example, during 2022–23, Seabees established Camp Tinian, an expeditionary camp on the island of Tinian that provides room to disperse U.S. joint forces in Guam and supports airfield improvements at Tinian International Airport. In the South Pacific, Seabees are supporting the Papua New Guinea Defense Forces by building out training, medical, and port facilities at Lombrum Naval Base on Manus Island.8
Besides constructing new expeditionary camps and building the capabilities of partner naval forces, Seabees maintain existing naval infrastructure critical to fleet operations. For example, in Sasebo in 2023, Seabee divers conducted emergency repairs to fueling piers, which suffered significant wear and tear during 80 years of use by the Imperial Japanese Navy, Japan Maritime Self-Defense Force, and U.S. Navy. They also surveyed existing and potential naval bases and informed the Seventh Fleet commander’s staff on the strategic laydown for future platforms.9
Conflict
While Seabees strive to prevent conflict by excelling in the cooperative and competitive phases of military operations, they stand ready and able to go into harm’s way and provide the fleet commander with critical infrastructure within the adversary’s tactical weapons engagement zone. Seabee units train and stand ready to enable a decisive naval victory in the western Pacific in the following ways:
• In support of Marine littoral regiments and their deployed expeditionary advanced bases (EABs), a waterfront construction company could be reinforced with a Seabee dive detachment and Marine heavy equipment section to repair and improve a neglected harbor. This could mean the difference between only being able to airlift supplies and shoulder-mounted missiles in ten-ton increments via V-22 Osprey, to being able to use amphibiously lift to move antiship missiles and air-defense platforms, which may weigh hundreds of tons. An EAB supported by a reinforced Seabee waterfront construction company could transition from point-defense to area air defense and even over-the-horizon maritime strike.
• An NMCB headquarters with a subordinate airfield construction company and advanced base construction company could provide in-depth perimeter defense of the air base and build prefabricated structures to create expeditionary refueling and rearming points for F-35Bs. Battalion-sized task forces also could disperse and stockpile repair materials, quickly recovering an alternate airfield’s operational capability after a missile barrage. Such elements would force the adversary into an operational dilemma, having to decide between expending costly precision munitions against a resilient airfield or giving the fleet commander a “free” node from which they could launch strikes.
• Slightly behind the contact layer, a UCT headquarters element could deploy to an empty atoll and be tasked to turn it into an anchorage at which expeditionary ship rearm and repair operations will be conducted. Two attached dive detachments could survey, blast channels, and install buoys, while the UCT’s operations officer—who holds a contracting officer warrant—directs a commercial engineering firm to dredge and lay tetrapods to build a safe haven in which damaged and depleted ships could anchor.
• An advanced base construction company specializing in expeditionary medical facility construction could build a 150-bed surgery-capable field hospital to treat casualties from intense fleet action.
Naval combat sorties in the western Pacific inevitably will strain installations, even those east of Guam. Islands farther east, such as Wake, may turn from sleepy Air Force refueling outposts into major intermediate staging bases, where sea- and airlifted military supplies will be transferred to tactical aircraft and vessels. A reserve naval construction regiment and subordinate battalions drawing personnel from the commercial construction sector could be best suited to efficiently transform a sleepy outpost into a major logistics hub. Combined with other Naval Expeditionary Combat Command units, such as Navy expeditionary logistics regiments, a reserve naval construction regiment could build a hub through which decisive amounts of “beans, bullets, bandages” would flow.
Born to Build and Fight
Seabees were born to “Build and Fight” in the Pacific during World War II and never stopped their service to the fleet and the Marine Corps. As national security priorities have evolved, the Seabees played their part in Korea, Vietnam, Iraq, and Afghanistan. As the Navy and the Marine Corps refocus their efforts in the western Pacific, the Seabees have again honed their capabilities and refurbished their doctrine to support the fleet where most needed. Whether the Navy deters and competes or fights a decisive naval campaign in the western Pacific, Seabees will build and repair the critical infrastructure that enables fleet maneuver.
1. Naval History and Heritage Command, “Seabee History: Formation of the Seabees and World War II,” 18 February 2006, www.history.navy.mil/research/library/online-reading-room/title-list-alphabetically/s/seabee-history0/seabee-history.html.
2. Commander, Navy Expeditionary Combat Command, “History of NMCB 133,” www.necc.usff.navy.mil/Organization/Operational-Forces/SEABEES/NMCB-133/History/.
3. Department of Defense, MCWP 4-11.5, “Seabee Operations In the MAGTF” (Norfolk, VA: Naval Doctrine Command: November 1997).
4. PO2 Austin Ingram, USN, Naval Mobile Construction Battalion 3 Concludes Field Training Exercise, Operation Turning, Commander, Navy Expeditionary Combat Command, 19 December 2023.
5. Director, Expeditionary Warfare, Required Operational Capabilities and Projected Operational Environment for the Naval Construction Force (Washington, DC: Office of Chief of Naval Operations, 6 February 2023).
6. CDR Roy A. Mosteller, USN (Ret.), “Robert Stethem, The United States Navy Memorial,” navylog.navymemorial.org/stethem-robert.
7. Palau Island Times Editorial Staff, “Palau ‘Wishes Fair Seas’ to Navy CAT, Welcomes Incoming Army CAT,” Palau Island Times, 16 February 2021.
8. Seth Robson, “Australia and Papua New Guinea Revive World War II-era Naval Base Built by Americans,” Stars and Stripes, 6 December 2021.
9. Public Affairs Office, Commander, U.S. Seventh Fleet, “UCT-2 Concludes Maritime Infrastructure Assessment in FSM,” www.c7f.navy.mil/Media/News/Display/Article/1846714/uct-2-concludes-maritime-infrastructure-assessment-in-fsm/.