Why a Carrier Aircraft Service Unit (CASU)?

During early 1942, as the war in the Pacific just began to unfold, US Navy leadership recognized they were going to need more than just aircraft carriers to launch airplanes against Japanese forces.   As Navy planners studied maps of the western Pacific they noticed thousands of islands that most of them had never heard of before and when their Intelligence officers started marking many of these islands with Japanese airports and runways some strategists began realizing that the path to Japan was going to be by “Island Hopping.”  This tactic, as it unfolded, consisted of US Marines performing amphibious landings on selected islands, followed by Navy Seabees repairing and improving the captured runways, and finally, Marine, Navy and Army Air Corp aircraft arriving to assist the Marines with their next island target.

Aircraft carriers carry on board, wherever they go, parts, fuel, ammunition and maintenance personnel – all the ingredients necessary to keep the planes in the air and ready to fight.  The newly captured, island based, Japanese runways, however, did not come with all of these necessary ingredients; all of the personnel, equipment, parts, and food to support an operational airport had to be delivered ready to go to work.  The CASU was part of the package designed to turn a Japanese airport into a US military airfield.  Quite often the island site where aircraft maintenance was required necessitated quick delivery due to the rapidly changing requirements of the war.  So, to support rapid transfer, the CASU was organized as a group of maintenance personnel without any equipment or tools.  An outfit, much larger than a CASU, called an “Acorn” was designed to go ahead of the CASU and perform rapid runway repair, installation and operation of the newly acquired island air base.  In this scheme it was the responsibility of the Acorn to provide all the equipment and tools needed by the CASU, however, as I will share in future Blogs, this did not always work out as planned.

For further understanding of the role of a CASU in the “Island Hopping” strategy, I am going to let the July 1944 and June 1945 issues of the Naval Aviation News magazine tell the rest of the story.

“The Combat Aircraft Service Unit, until recently known as Carrier Aircraft Service Unit, is a wartime development, providing an extremely mobile organization to keep land-based Navy planes repaired.

They work hand-in-hand with an Acorn.  The Acorn’s Seabee battalion constructs the air strip and base facilities.  After the island air base is completed, the Seabees move on but the Acorn stays to operate the field.  Squadrons fly in with planes and the CASU keeps the planes operating.

There are two types of CASU’s today, those based in forward areas west of Hawaii being given the designation CASU (F).  Because it is a highly mobile unit, the CASU is not burdened with equipment.  This belongs to the Acorn.  The CASU remains in commission as a separate entity while the Acorn may be decommissioned and absorbed into an air base after it has been completed.

It is the function of a CASU to service, rearm, and make minor repair on land planes or seaplanes, large or small.  It maintains facilities and equipment in its charge, including personnel facilities.  The CASU also may furnish berthing, messing and service to personnel of air units, both flight and ground personnel.

Most CASU in the Navy are based overseas, although there are a number of larger ones on the continent at San Diego, Alameda, Seattle, Quonset, and Norfolk.  The standard CASU complement is 17 officers and 516 men, about a third the size of a standard Acorn.  Both, however, vary widely according to the size of the job they will have at their island base.

Because it is a self-contained unit, a CASU has a complete inner organization of its own, consisting of an engineering division, operations division, ordnance, radio and radar, supply, personnel and medical.  Engineering division looks after aircraft repairs, the main function of a CASU.  Operations handles all matters concerning operation of planes attached to or visiting the CASU.  Ordnance handles rearming and guns.  Radio and radar division repairs electronics gear.  Supply division looks after supplies and disbursing.  Personnel is assigned the job of handling officers and men of the CASU, including physical education and recreation.

CASU’s on advanced Pacific islands run into the same kind of rugged living conditions as frontline troops.  Long hours of night work repairing carrier-type planes, sleepless nights filled with bombings, cold food, disease, casualties, foxholes – all of these are a daily chapter in the kind of warfare they are running into.  Many units landed right behind the Marines and had to build their bases from scratch before they could start maintaining planes.  Their problems are much different from those confronting CASU’s operating on the continent, Squadrons had a habit of dropping in before the official reception committee was all set, supplies were delayed and replacement parts lost, but the CASU’s kept the planes flying, helping to push the Jap back toward Tokyo.”

Sources:  Naval Aviation News – July 1944 and June 1945 issues

WebSites:  http://www.history.navy.mil/nan/backissues/1940s/1944/1jul44.pdf


And a superb overview on CASU operations can be found at:


See Vern A. Miller’s article titled Our Coral Carriers Helped Turn the Tide of Battle

This ends today’s Blog – I continue to actively research CASU 11 and would welcome any and all information you might have about this specific unit – my email is william.h.little@gmail.com.  Hope to hear from you soon.

One thought on “Why a Carrier Aircraft Service Unit (CASU)?

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s