<p>The continuing battle fought between the US Army Air Corps and the US Navy was long and bitter, and no single issue was more vigorously contested by the US Navy than the repeated argument that the USAAC, with suitable aircraft, could more economically and effectively defend the nation's enormous expanse of coastline than could the US Navy with surface vessels. Constant dripping is said to wear away a stone, and by the early 1930s the US Navy relented sufficiently to allow the USAAC to explore its beliefs.
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<p>In 1934, therefore, the USAAC's Materiel Division issued its Project 'A' specification for a long-range bomber which could be used, if necessary, to provide support to troops in Alaska, Hawaii or Panama, this requiring the carriage of a 2,000-lb (907-kg) bomb load at a speed of 200 mph (322 km/h) over a range of 5,000 miles (8,047 km). It was certainly very much of a challenge at a time when aircraft manufacturers had not then succeeded in creating a civil airliner to cope with the North Atlantic.
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<p>Boeing responded with its Model 294, of which a prototype was ordered under the designation XBLR-1 (Experimental Bomber Long Range—1), later XB-15. The proposal received from Douglas was for a very much larger aircraft, and a single prototype of this was contracted as the XBLR-2, later XB-19. When completed, it was then the largest aircraft built, with accommodation for a crew of 10 and maximum bomb load of 36,000 lb (16 29 kg). It flew for the first time on 27 June 1941. Powered by four Wright R-3350-5 Cyclone 18 engines, each with a take-off rating of 2,000 hp (1,491 kW) and maximum continuous rating of 1,700 hp (1,268 kW) at 5,700 ft (1,740 m), it was underpowered for the duty required of it, and had to await the availability of more powerful engines. When these eventually materialized, the requirement had changed, and the Douglas giant was provided instead with four Allison inline engines and operated in a transport role during World War II under the designation XB-19A.
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<hi style=hdr1>Specification</hi>
<list style=aflst>
<item><hi format=bold>Type:</hi> long-range heavy bomber prototype
<item><hi format=bold>Powerplant (XB-19A):</hi> four 2,600-hp (1,939-kW) Allison V-3420-11 inline engines
<item><hi format=bold>Performance (XB-19):</hi> maximum speed 209 mph (336 km/h); cruising speed 186 mph (299 km/h); service ceiling 22,000 ft (6,705 m); maximum range 7,750 miles (12,472 km)
<item><hi format=bold>Weights (XB-19):</hi> empty 82,253 lb (37,309 kg); maximum take-off 164,000 lb (74,389 kg)
<item><hi format=bold>Dimensions:</hi> span 212 ft 0 in (64.62 m); length 132 ft 0 in (40.23 m); height 42 ft 9 in (13.03 m); wing area 4,492 sq ft (417.31 m<su>2</su>)
<item><hi format=bold>Armament (XB-19):</hi> two 37-mm cannon, five 0.50-in (12.7-mm) machine guns and six 0.30-in (7.62-mm) guns, plus up to 36,000 lb (16,329 kg) of bombs
