Designation: Douglas A-26 / B-26 Invader
Classification Type: Light Bomber / Heavy Assault Aircraft
Contractor: Douglas Aircraft Corporation - USA
Country of Origin: United States
Initial Year of Service: 1944
Number Built: 2,452

The Douglas A-26 Invader was a distinguished twin-engine light bomber whose origins were well-placed in the Second World War. The system proved adept at day and night flying, attacking targets with a bevy of machine guns or drop bombs and operating at low and medium altitudes with equal success. The type was fielded throughout the conflict in both Pacific and European theaters and went on to see action in the global wars to follow including Korea, Indo-China and Vietnam. In the end, the Invader served American forces for some twenty years before being officially retired and removed from service - such was the reach of this magnificent airplane.

Development
With design beginning as early as 1940, the Invader was first flown on July 10th, 1942 as the XA-26 pre-production prototype. The XA-26 appeared as a successor to the Douglas A-20 Havoc, an aircraft of similar role and design layout and featured a glass nose and 5,000 of internal and external ordnance capability. Armament consisted of 2 x 12.7mm forward-mounted machine guns and a remote-control periscope-fired dorsal and ventral barbette, each with 2 x 12.7mm machine guns (an arrangement very similar to the production A-26C models). A mockup was completed and showcased in early 1941 with the contract finalized in June of that year. The contract originally called for just two prototype aircraft types that included the XA-26 light attack bomber and the XA-26A dedicated night attack fighter.

The resulting tests revealed some structural issues with the nose landing gear - it proving prone to collapse - and, as such, the component was redesigned. Other modifications centered on engine overheating to which the original propeller spinners (intended to promote streamlining of the aircraft) were removed for improved cooling airflow and the engine cowlings were redesigned for better performance. Overall, the tests proved the aircraft design sound and capable of great speed. Handling was regarded as above average and very responsive. What made the XA-26 unique was its single pilot cockpit, not requiring the need for a dedicated co-pilot and thusly keeping the fuselage a slender shape ala the Northrop P-61 Black Widow and Douglas A-20 Havoc. The XA-26 was ordered by the USAAF with the series designation of A-26 and consisted of several major variants, though no A-26A production model existed. Production of the A-26 series progressed slowly as most of Douglas' plants were tied to previous contract aircraft production. As such, the A-26 would have to wait until 1944 to see any complete forms.

The XA-26A model was a prototype night-fighter and attack platform. This model deserves mention for its dedicated role introducing the solid nose covering the search radar system. A ventral gun tub was devised to compensate for the aircrafts lack of forward armament and resulted in a battery of 4 x 20mm cannon. Bombload was a diminutive 2,000lbs thanks to the space committed to the radar system and cannon armament (and ammunition). The dorsal remote-controlled barbette was retained with its 2 x 12.7mm machine guns. The Northrop P-61 Black Widow beat the XA-26A to the night-fighter punch, being already in production and offering the same performance specifications as the XA-26A. Power was to be from a pair of Pratt & Whitney R-2800-27 radial engines rated at 2,000 horsepower each. The XA-26A existed in just a single prototype offering.

In June of 1942, the initial Army Air Corps contract was amended to and added a third prototype aircraft in the form of a single XA-26B example completed at the Douglas El Segundo plant. This aircraft model was to fit the mold of low-altitude attacker platform with Pratt & Whitney R-2800-27 engines of 2,000 horsepower each and an internal/external bomb capacity of 6,000lbs with a crew of three. Visually, the XA-26B was similar to the XA-26A model series and featured a similar solid nose covering but this over an embedded 75mm cannon. In theory, the aircraft proved a sound weapon but in practice, the cannon was slow to fire and prone to jamming with a high level of required maintenance. This forced the Douglas team to try a host of alternative armament combinations including the use of 37mm cannon or heavy machine guns or both. Some early production B-models were pulled off the line for testing various armament load outs. Impressive ideas were covered but proved fleeting such as mounting the 75mm cannon with two 12.7mm machine guns or twin 37mm cannons with 4 x 12.7mm machine guns. This developmental delay eventually resulted in an early batch of production B-models fitted with 6 x 12.7mm machine guns and a later block of production B-models with 8 x 12.7mm machine guns as production of the type had already begun while testing of the armament ensued. The USAAF accepted the design on June 30th, 1943.

The A-26B model series became the production version of the XA-26B, with its mounted collection of heavy machine guns in a solid nose assembly and a top speed of 350-355 miles per hour with her Pratt & Whitney R-2800-27, -71 or -79 series engines of 2,000 horsepower. A crew of three operated this type and consisted of a pilot, navigator/loader and gunner. Some 1,355 B-26B model series aircraft were eventually produced along with 25 other aircraft that were never delivered. Production was handled at two Douglas plants - one in Long Beach, California and the other in Tulsa, Oklahoma.

These Invader models were eventually followed by an A-26C model with a glassed-in nose and bombardier-manned Norden bombsight along with a top speed increase to 370 miles per hour. These were more in line with the dedicated light attack bomber role than the preceding A-26B models, whose forte was generally strafing with machine guns. A-26C models were built concurrently alongside A-26B systems. Early A-26C's were seen with a framed cockpit but this was later changed to the clamshell type glass cockpit, improving both range and emergency exiting of the aircraft. C-models were fitted with more powerful engines in the form of 2 x Pratt & Whitney R-2800 engines of 2,000 horsepower each with water injection. Wings were also strengthened to mount up to 14 x 5" rockets or 2,000lbs of bombs. The wings were slightly altered to accommodate 6 x 12.7mm wing-mounted machine guns to make up for the lack of punch caused by the removal of the nose-mounted armament common to the B-models. 1,091 A-26C models were delivered.

A-26C models had a distinction in becoming "lead ships" for solid-nose A-26B models. As lead ships, the A-26C would register its target and drop her bombs, signaling the trailing A-26B's to do the same. This method of bombing proved commonplace for aircraft in the light bombing role such as the A-20 Havoc. A-26C models eventually replaced the specially designed A-20 Havoc lead ships (A-20J's and A-20K's) in this role.

RB-26B and RB-26C represented unarmed photo reconnaissance models modified from existing B-26B and B-26C models respectively whereas trainer B-26's were designated as TB-26B and TB-26C based on their respective letter models. VB-26B served in an administrative role. Post-war production Invaders were to spawn from the proposed A-26Z configuration which would have covered both a solid nose A-26G and glass nose A-26H model. These were never produced. The US Navy utilized a few Douglas Invaders in limited roles and designated them as a target tug series JD-1. Drone directors were known as JD-1D with both redesignated in 1962 as UB-26J and DB-26J respectively. The YB-26K was a highly-modified B-26B model, becoming the B-26K "Counter Invader" and ultimately redesignated back to the A-26A. These two-man aircraft flew with Pratt & Whitney R-2800-103W engines of 2,500 horsepower with water injection and operated in the Vietnam War.

Design
Design of the A-26 Invader was typical of light attack bomber design in the Second World War. The fuselage was streamlined and contained the cockpit, bomb bay and gun positions. The nose on the B-26B was a "solid" nose when utilizing the 6 or 8 x 12.7mm machine gun arrangement. The glassed-in nose found on A-26C models indicated the use of a bombardier/navigator and bombsight controls in place of the nose-mounted guns. An Invader crew of three traditionally consisted of the pilot, navigator/radio operator and gunner, the latter manning dorsal and ventral gun turrets. The C-model featured a bombardier/navigator crewmember along with two nose-mounted 12.7mm machine guns. The airframe proved a well-put together structure as many an Invader was known to receive substantial amounts of damage and still return her crews to home bases. Flying on a single engine was possible, this occurring even with a full bombload. The empennage was traditional and featured the identifiable rounded vertical fin extending from the upper aft fuselage.

Armament
The A-26B Invader shined when it came to its armament loadout. More noticeable was the battery of 6 x 12.7mm (.50 caliber) heavy machine guns (early block A-26B models ) all allocated in the nose housing. Later block B-26Bs featured a total of 8 x 12.7mm nose-mounted machine guns. This assembly allowed the Invader to make devastating strafing sweeps on enemy ground targets with usually destructive results, combining the concentrated power of six to eight heavy caliber machine guns into one focal burst of hot lead. In addition to the nose armament, two 12.7mm machine guns were held in a dorsal barbette while another two were featured in a ventral barbette. The ventral barbette was sometimes removed in favor of an additional fuel cell. Invaders could also sport 8 x underwing gun pods and 6 x 12.7mm machine guns mounted in each wing leading edge (three guns to a side) along with blister mounts on the fuselage sides - all concentrated in a forward-firing position. With a single burst of the all machine guns, the entire aircraft would buffet violently rearward, a consideration for the crew to keep in mind in terms of their own safety. In total, a given A-26 could sport as many as 22 x 12.7mm machine guns with up to 6,000 rounds of ammunition.

The Douglas Invader's lethality was furthermore accented by the option of carrying between 4,000 and 8,000lbs of internal and external ordnance in the form of drop bombs or 8 to 14 x 5" rockets (the latter held externally on eight or fourteen underwing pylons - the full 16 rocket deployment was achievable in lieu of the drop tanks and wing mounted bombs). In fact, Invaders were known to be able to carry greater bombloads than that as found on the larger Boeing B-17 Flying Fortresses. Endurance could be extended with the addition of 165-gallon underwing drop tanks, increasing the aircraft's range by up to 300 miles. C-model Invaders with the glassed-in nose were fitted with 2 x 12.7mm machine guns in the nose along with the 2 x 12.7mm gun systems in each turret but forward firepower was augmented with the addition of the 6 x wing-mounted machine guns.

Operational Service
Deliveries of the A-26 in the B-26B model form began in August of 1943 and the system instantly became the fastest American bomber of World War 2. The system saw extensive action in varying roles throughout the conflict both in the European Front and along the Pacific Front. A-26's were put into action with the Fifth Air Force in the Pacific Theater and flew their first sortie on June 23rd, 1944. European deliveries occurred in September of 1944 and were stationed with the Ninth Air Force, seeing their first combat sorties just two months later. Invaders served through to the end of the war to which many served in the post-war world with the United States Strategic Air Command and Tactical Air Command. The USAF dropped the "attack" designation of the aircraft in 1948 and officially redesignated the Invader as the B-26 (not to be confused with the World War 2-era Martin B-26 Marauder medium bombers).

The A-26B and A-26C saw extended use in the upcoming Korean War with at least 37 aircraft in hand on June 25, 1950. Elements of the 3rd Bombardment Group (8th, 13th and 90th Squadrons) were some of the first units put into action in the conflict, launching from Japanese bases to strike targets on the peninsula. Later that year, group strength increased to 90 aircraft. These Invaders could be counted on to operate at low levels in the dark of night, maneuvering over and around the dangerous mountain terrain in Korea. Invaders would be credited with thousands of enemy vehicles destroyed by the end of the war, totaling some 232,000 flight hours and close to 20 million rounds of 12.7mm ammunition fired. Initially, Invaders stationed in Japan were intended to provide cover fire for US citizens evacuating the South Korean capital of Seoul. But by June 29, 1950, the aircraft was directly hitting North Korea targets as required. The B-26 proved an invaluable asset in the disruption of supply lines running along known roads where the Invader could bring the brunt of its firepower to bear on unarmored targets. Tactics changed with operational experience and Invader crews learned to bomb with precision those moving targets that they may have - in past sorties - attempted to strafe with their guns. Invaders targeted airfields with equal fervor, utilizing their formidable bombloads (including napalm) along with their machine guns and rockets against targets of opportunity. The A-26 itself proved a success in its night missions though the foe proved undoubtedly resilient, able to change their routing patterns on the ground in reaction to American attack patterns.

B-26 aircraft would also be the last USAF aircraft to drop ordnance in the conflict before the cessation of hostilities. After the war, a North Korean general would admit that the B-26 was one of the most feared weapons of the conflict - such was its terrorizing reach on ground targets at night. At least 7 B-26 squadrons were stationed for action in the Korean War including one RB-26 element. American B-26 models were temporarily removed from service in 1958 and served in strictly liaison mission and staff transportation roles.

France became another Invader operator, utilizing the USAF on lease in their Indo-China conflict of the 1950's. These carried the unofficial designation of B-26N and were based on B-26C models with AI Mk X radar systems from old Meteor NF.11 jet-powered night-fighters. French systems operated their Invaders with gun pods and underwing rockets.

American B-26B systems were called to action once again, this time in 1961 with the USAF as tactical bombers in the early years of the Vietnam War. President John F. Kennedy's assistance initiative called the aircraft back into action from storage and the Invader was brought online in reconnaissance and attack roles. This action was short-lived, however, as the systems fought from 1961 through 1964. Aircraft taking part in this early action actually fought with South Vietnamese markings and under RB-26 reconnaissance designations but were fully combat ready. Missions of the aircraft soon grew to include escort and close air support along with traditional attack roles. By this time, the war-weary B-26's began to show their age. Years of operational use began to take their toll on airframes as constant operation decreased the overall safety of the type. The B-26B was soon withdrawn from service for safety's sake, as the crash of at least two such aircraft from structural failure necessitated the move.

In 1963, at least 40 B-26 aircraft became the two-seat B-26K "Counter Invader" model for the USAF following the successful trials of the YB-26K program. The YB-26 featured water injection Pratt & Whitney R-2800-103W engines of 2,500 horsepower, 8x 12.7mm nose machine guns, 6 x 12.7mm wing machine guns with external pylons for up to 8,000lbs of ordnance, an internal capacity of 4,000lbs and dual cockpit controls with updated avionics.

With modification handled by On Mark Engineering Company, these aircraft appeared in production form with Pratt & Whitney R-2800-52W engines with water injection, reversible propellers, reinforced wings with modified wing flaps, rebuilt tail section with larger rudder and wingtip fuel tanks for increased endurance. Additionally, these B-26K models had their 6 x 12.7mm wing-mounted machine guns removed but retained the formidable 8 x 12.7mm formation in the solid nose assembly. These Invaders, like their Korean brethren, were charged with disruption of enemy supply lines. In 1966, these B-26K models were now officially redesignated as A-26A. in Counter Invaders operated in Southeast Asia up until 1969 before retirement from the USAF. By this time, the role of the A-26A was overtaken by the cannon-laden Lockheed AC-130 Hercules gunships among other more capable aircraft. Production of the B-26K/A-26A occurred between 1963 and 1964 at a unit cost of $577,000.

The final A-26 was retired from service in 1969 and the entire line was removed from service by 1972. Some 2,452 Invaders were produced. In all, 18 different countries operated the Invader at one time in civilian and military guises.

A-26's also served with US Air National Guard units, becoming some of the final American users of the aircraft. ANG units received their Invaders in the post-war years. This was abruptly abandoned at the start of the Korea Conflict as B-26's were earmarked for war once again. With the jet age progressing and the Korean War drawing to a close, A-26 deliveries continued to the ANG which operated the type throughout the 1950's. The B-26 would see its last noticeable ANG occurrence in early 1970 as a converted staff transport.

Conclusion
The Douglas A-26/B-26 lived a very long and productive operational life considering her origins in a World War 2 requirement. Not only taking part in that conflict, the Invader saw prolonged use and unnatural long life for a bomber in the ensuing Korean and Vietnam Wars. In any case, the Invader retained many of the qualities that her crews admired - speed, survivability and offensive firepower. The system endured for decades since its inception and went on to prove her mettle in conflicts that tested most any other machine in the skies - leaving the fabled Invader to pass with flying colors.

Factoids
• Design of the aircraft is credited to Edward Heinemann, Robert Donovan and Ted R. Smith.
• A-26/B-26 Invaders were operated by Cuban exiles during the failed Bay of Pigs Invasion of 1961.
• The Invader fought on in varied forms through World War 2, the Korea War and the Vietnam War.
• The A-26 Invader was redesignated to B-26 in 1948, then later back to its original A-26 designation.
• Though designated the Douglas "B-26" - in much the same way as the Martin "B-26" Marauder, this designation change occurred well after the use of Martin's aircraft was discontinued so no apparent confusion between the two types were made.