The Expeditionary Sea Base Vessels (ESB)
With its open mission deck and overhead flight deck amidships, the Expeditionary Sea Base (ESB) gives the United States’ special operations forces a floating platform to conduct special operations, minesweeping, rotorcraft repair, refueling, and arming, and expeditionary warfare missions. ESBs can transport boat trailers and military shipping containers and Mission Modules with various mission configurations such as cargo, medical, drones, counter-drone, surveillance, and sensors.
ESBs are based on the civilian Alaska-class oil tanker hull and have a sustained speed of greater than 15 knots, a range of 9,500 nautical miles at 15 knots, and displace 90,000 tons. They are 239.3 meters (785 feet) long with a beam of 50 meters (164 feet). ESBs have no armor or automatic close-in weapons systems; however, self-defense comes from 12 crew-operated .50 caliber heavy or 7.62mm M240B medium machine gun mounts at various positions.
Regarding facilities, ESBs contain fuel and equipment storage accommodations, weapon magazines, explosive ordnance disposal magazines, mission-planning spaces, a flight briefing room, tactical command and communications center, a gym, medical facilities, mess halls and kitchens, berthing (34 crew and a 250 military detachment), hangar, ship store, planning and control spaces for Airborne Mine Countermeasures (AMCM), and underway replenishment facilities.
The flight deck has space for four rotorcraft with two more in the hangar and can accommodate the U.S. Marine Corps’ (USMC) CH-53 for vertical airborne assault or the U.S. Navy’s MH-53E for airborne minesweeping. The flight deck only supports helicopters and tiltrotors as the ESBs do not have the aviation, lighting and signaling, and air traffic control facilities built in to accommodate the USMC’s F-35B vertical takeoff and landing stealth fighter.
As of early 2024. there are six ESBs in service or in various stages of construction: USS Lewis B. Puller (ESB 3), USS Hershel “Woody” Williams (ESB 4), USS Miguel Keith (ESB 5), and follow-on ships John L. Canley (ESB 6), Robert E. Simanek (ESB 7), and Hector A. Cafferata Jr. (ESB 8). ESBs 3 to 6 have been delivered to the U.S. Navy and ESBs 7 and 8 are currently under construction.
“The ESBs provide useful and highly demanded capabilities at a cost far below traditional amphibs,” wrote Mark Cancian, retired U.S. Marine Corps colonel and Senior Adviser, International Security Program, to the Center for Strategic and International Studies (CSIS) via email to Naval News. “They can perform a wide variety of missions, from special ops to mine countermeasures in medium to low-threat environments. They allow traditional amphibious ships, which are built to military specifications, to focus on those missions that require that high level of capability.”
USSOCOM Comments on ESB
In late January 2024, Naval News asked the United States’ Special Operations Command (USSOCOM) what they see valuable in the ESBs.
“The Expeditionary Sea Bases (ESBs) provide a flexible, global capability that augments Special Operations Forces’ (SOF) Afloat Forward Staging Base (AFSB) requirements but are not sufficient as standalone AFSBs for most types of operations that we execute,” said the USSOCOM spokesperson via email. “At times there may be a need to augment on-board equipment, which is determined by mission requirements”.
“ESBs are predominantly used for overflow deck space requirements when other naval vessels or the SOCOM Maritime Support Vessel cannot meet the deck space requirements for their missions. The biggest benefit of utilizing the ESBs is that they are not always fully engaged in operations, which provides the flexibility to direct their positions to meet emerging mission requirements. This gives SOCOM the ability to support a wide range of operations and adds significant value to SOCOM’s integrated deterrence capabilities.“
U.S. Special Operations Command spokesperson
Naval News asked the spokesperson what the SOCOM Maritime Support Vessel is and the spokesperson replied that he would look into the inquiry but the answer was not revealed before publication. Nonetheless, TheWarZone has a story on the SOCOM Maritime Support Vessel.
Before the ESBs were built, USSOCOM solely relied on the U.S. Navy’s amphibious ships such as Dock Landing Ships (LSDs) and Landing Platform Docks (LPDs). AFSB USS Ponce (LPD 15) was the precursor to the ESB design and LPD 15 decommissioned in October 2017 after 46 years in service.
A USSOCOM rotational tour on the ESB is determined by mission requirements and USSOCOM declined to give an exact segment of time.
What Have the U.S. Navy’s ESBs Hosted?
USSOCOM declined to comment on the milestones and achievements that the ESBs have achieved for the United States’ special operations forces. However, official military photos and interviews with U.S. Navy personnel have confirmed that ESBs have hosted U.S. Army, Navy, Marine Corps, and special operation forces’ cargo and attack helicopters and foreign rotorcraft on its flight deck. V-22s have also landed and taken off from the flight deck.
Watercraft carried aboard include rigid hull inflatable boats, combat rubber raiding crafts, USSOCOM Combat Craft Assault, and various types of unmanned surface vessels.
ESBs have also participated in U.S. Marine Corps’ ground force exercises and trained various special forces operators and Fleet Antiterrorism Forces. Navy medics have also visited the ESBs in addition to foreign military personnel.
