Engineer Amphibian Group (United States)

The Engineer Amphibian Group (EAG) is a regiment-sized amphibious unit type of the United States Army. Current day EAGs trace their lineage back to the Engineer Boat and Shore Regiments of the Pacific War, but today are affiliated with the Engineer Regiment the same as most other military engineering units.

Their purpose is to operate the U.S. Army's watercraft—including logistics vessels, lighters, landing craft, and riverine patrol boats—and provide the appropriate construction units to construct shore terminals and mobile piers. During terminal operations Engineer Amphibian Groups operate closely with Port Battalions of the Transportation Corps that operate the land side of water terminals and coordinate watercraft movements. Normally one Port Battalion can operate one water terminal and the EAG can support several ports. The EAG normally operates under a Corps Support Command or army-level Transportation Brigade, but may be placed under a Combined Amphibious Command under U.S. Navy leadership for amphibious operations. During amphibious operations U.S. Army units from other branches, such as Amphibious Truck Companies from the Transportation Corps or Amphibious Medical Battalions, may be task organized under an Engineer Amphibian Group as the Army's ship-to-shore movement authority before the establishment of a water terminal.

Control over watercraft and amphibians has been debated over by the Corps of Engineers and Transportation Corps for nearly a century. The status quo division of responsibility was decided on in the 1970s. Since then the Transportation Corps has been responsible for port operation, movement control, onward movement of material, and the actual operation of amphibians with carrying capacities below 15 tons (called "amphibious trucks") while the Corps of Engineers has been responsible for port construction and the operation of watercraft, including large amphibians rated to carry 15 tons and above (called "lighters, amphibious, expeditionary" or LAX).

Units and composition

There are currently four Regular Army EAGs and two Organized Reserve EAGs:

• 531st Engineer Amphibian Group, IX Corps Support Command
• 532nd Engineer Amphibian Group, I Corps Support Command
• 564th Engineer Amphibian Group, 2nd Transportation Brigade, 1st Theater Army Area Command (U.S. Army Pacific)
• 594th Engineer Amphibian Group, 12th Transportation Brigade, 6th Field Army Support Command (Sixth Army)
• 598th Engineer Amphibian Group (ORC Class B), IV Corps, Northwest Army Area
• 599th Engineer Amphibian Group (ORC Class A), 3rd Transportation Brigade, X Corps, Northeast Army Area

Each Engineer Amphibian Group consists of a varying number of amphibian or boat battalions, which in turn provide oversight for numerous boat (harbor, medium, heavy), landing craft, barge, and barge crane companies and detachments. These subunits are usually task organized in Watercraft Task Forces to support the needs of a specific port terminal. While most of its watercraft companies are designed solely for uncontested logistics-over-the-shore operations, landing craft companies support the U.S. Army's amphibious warfare capability and train closely with the U.S. Navy. Each EAG also has one Multipurpose Engineer Battalion with the ability to support the establishment of two water terminals simultaneously or provide detachments in assaulting waves to clear beach obstacles and ease the movement of heavy army equipment.

The 564th Engineer Amphibian Group is unique in that its 1st Battalion is the U.S. Army's only Special Assault Boat Battalion. It operates small high performance watercraft designed to support the U.S. Army's unconventional and special forces through riverine insertions and extractions, fire support, and search and rescue. It is the equivalent to the U.S. Navy's Special Boat Units.