The Army became very much interested in the Allison engine. Although a number of Army fighters were equipped with radials following the early successes of that type of engine, Air Corps men believed that, due to its narrow frontal area, the in-line engine could help to streamline fighters. Finally, in 1939, after many changes, the first Allison engines were installed in Curtiss P-40 Army fighters. The first Allison engine had developed 1,090 horsepower. By 1940 its horsepower was increased to 1,150 and the Army adopted it as standard. It was installed in all P-40’s and later in Lawrence Bell’s P-39 _Airacobra_. In the P-39 the engine was installed in the fuselage behind the pilot. A ten-foot shaft carried the power to the propeller in the nose of the ship. This installation permitted the housing of a 37-millimeter cannon and two machine guns in the nose of the _Airacobra_. The Lockheed P-38 _Lightning_ was powered with two Allison engines, making it the first fighter with more than two thousand horsepower. [Illustration: LOCKHEED P-38 _LIGHTNING_] [Illustration: ALLISON LIQUID-COOLED, V-TYPE, IN-LINE, 1,150-HP. 12-CYLINDER ENGINE.] [Illustration: BELL P-39 _AIRACOBRA_ WITH THE ALLISON ENGINE INSTALLED BEHIND THE PILOT’S COMPARTMENT.] BATTLESHIPS OF THE AIR LEAD THE WAY TO VICTORY Regardless of the fact that this country was at peace and our military policy a defensive one, our farseeing Air Corps leaders continued to build American air power around the heavy, long-range bomber. As the heavy bomber was primarily an offensive weapon, many Americans believed the Army’s development of it to be contrary to our declared policy. As a result, we did not build great numbers of bombers. However, with the small number that we did have, our Army aviators made great progress in the technique of high-altitude bombing. As in all branches of the United States Army, great stress was laid on good marksmanship. Army aviators were trained to hit the mark with their bombs just as the infantryman does with his rifle. Other countries developing heavy bombers were satisfied if their airmen dropped a great many bombs in a given target area. In this country the development of the bombsight enabled our aviators to hit a target with great accuracy from high altitudes. This is called precision bombing. It was also known as pin-pointing a target, because of the ability of our bombardiers to score direct hits on small targets. It was the B-17 _Flying Fortress_ that gave Army airmen the greatest help in perfecting high-altitude, precision bombing. The broad wings of the _Fortress_ furnished a steady platform from which to aim the bombs, and the great plane was able to fly smoothly in the higher altitudes. The bombardier riding in its transparent nose could carefully line up his target and drop his bombs with precision accuracy.