CAMP KINSER, Okinawa, Japan – Marines and Sailors from 3d Marine Logistics Group and Naval Mobile Construction Battalion 4 successfully completed exercise Poseidon’s Watchtower 21 today. The exercise took place June 2-17, 2021, on the islands of Ukibaru and Irisuna, Okinawa, Japan.

PW-21 served as an opportunity for the Marines and Sailors from 3d Landing Support Battalion, 9th Engineer Support Battalion, and Marine Heavy Helicopter Squadron 462 to support NMCB-4 Sailors, known as Seabees, to rehearse and refine the concepts of naval integration and Expeditionary Advanced Base Operations.

EABO, a major focus of 38th Commandant of the Marine Corps Gen. David H. Berger’s 2019 planning guidance, depends on the ability of low-signature forces to operate from key terrain in support of maritime maneuver.

On Irisuna, the Navy-Marine Corps Team constructed a bunker utilizing low signature materials from the natural resources found on the island. The exercise served as a proof-of-concept for the capabilities of the Seabees and tested the coordination and teamwork efforts of 3d LSB, HMH-462, and 9th ESB. High-Speed Transport vessels and CH-53E Super Stallion heavy transport helicopters delivered personnel, supplies, and equipment to the island. Marines and Seabees then got to work excavating the 5-foot deep site location, mixing and making rebar-reinforced concrete, and constructing the bunker.

“Poseidon’s Watchtower 21 gave the Navy-Marine Corps Team an opportunity to practice EABO concepts by identifying an island with no prior infrastructure and constructing a bunker in a logistically constrained environment,” said Lt. Cmdr. Steve R. Bischak, operations officer of NMCB-4. “This is the first time since Guadalcanal that we’ve been able to integrate our combined efforts in this manner. As part of the planning cycle, our results feed the follow-on engineering operations that would occur.”

On Ukibaru, PW-21 tested the Naval Engineering Force’s ability to perform engineering reconnaissance of near shore hydrography through the shore to inland. Navy divers with Underwater Construction Team 2 reconnoitered the coral shelf to search for entry points capable of facilitating the passage of a Light Amphibious Warship or an Extra Large Unmanned Undersea Vehicle. Meanwhile, Seabees from NMCB-4 employed a Light Detection and Ranging machine, a mobile three-dimensional imaging platform, to gather accurate terrain information that would otherwise not be available by conventional means.

"The combined Navy & Marine Corps engineering reconnaissance efforts on Ukibaru showcased our ability to integrate as a joint naval force to meet the mission,” said Ensign Darek C. Ditto, the officer in charge of the Seabees on Ukibaru. “The reconnaissance teams from NMCB-4, UCT-2, and 9th ESB conducted proficient data collection that will be utilized to support the conceptual design of a littoral transition point used to refuel and resupply fleet assets.”

The Marines of 9th ESB tested the efficacy of the Engineering Reconnaissance Team, which blends the subject matter expertise of intelligence, logistics and demolitions. The ERT, working closely with the Seabees, combined their expertise to assess the island’s suitability for a variety of missions, from refueling and resupply, to long-range precision fires via a High Mobility Artillery Rocket System.

“The mission of the Engineering Reconnaissance Team was to evaluate the island and establish if it met the requirements to provide logistical support in the island chain,” said 1st Lt. Brandon A. Cavil, the officer in charge of the ERT on Ukibaru. “We wanted to use Poseidon’s Watchtower to practice our ability to establish simulated EABs in advantageous and austere locations in order to increase the logistic throughput in support of military operations.”

3d MLG, based out of Okinawa, Japan, is a forward-deployed combat unit that serves as III Marine Expeditionary Force’s comprehensive logistics and combat service support backbone for operations throughout the Indo-Pacific area of responsibility.

Photo Caption: Construction Electrician 3rd Class James Fuerneisen, assigned to Naval Mobile Construction Battalion 4, pours sand into a mixer to create concrete that will be used in the construction of a bunker on W-174 Joint Okinawa Training Range Complex, an uninhabited island off the coast of Okinawa, Japan, as part of joint exercise Poseidon’s Watchtower. Poseidon’s Watchtower is a multi-domain exercise designed to simulate the establishment of Expeditionary Advanced Bases through joint service integration.