The use of airplanes to drop things that go "BOOM" dates back to the early years of the Great War, when observation pilots in cloth-covered biplanes started chucking explosives out of their cockpits while over enemy territory. By the time the Great War ended, the heavy bomber was in use by both sides, from the British Handley Page Type 0 to the German Gotha G.IV. But was in the inter-war years that the first modern heavy bombers were designed, and of those, there is one that stands out.
In 1936, bomber wings in the United States Army Air Corps were beginning to take delivery of a new bomber. The new four-engine heavy bomb-hauler was based on Boeing's Model 299; the big warbird could haul a 4,800-pound payload and was defended by five .30 caliber machine guns. These were the original marks of the Flying Fortress, the YB-17, YB-17A, the B-17B, B-17C, and B-17D, which lacked the gun turrets and tail gun position that later marks of the Boeing great had.
In late 1941, this was identified as a shortcoming in this warbird in a time where 1) war was on the horizon, and 2) there was no fighter in the arsenal that could escort the long-range heavy bomber to its target and back. The Army dealt with this in classic, time-honored American faction: by sticking more guns on it. Bigger guns, too, as later marks did away with the .30 caliber machine guns in favor of big .50 caliber Brownings.
More guns, after all, are always better than fewer guns. This is the second of two great military laws, the first being that "There is no problem that cannot be solved with a suitable application of high explosives" and "There is no such thing as too many guns." The B-17 combined both of these great laws in one big, handsome four-engined package.
The B-17E, introduced in 1941, revised the side gun ports and added a rotating Sperry top turret, a Sperry ball turret in the belly, and a tail gun position. Most had one or two machine guns stuck in "cheek" positions in the front of the fuselage as well. In this iteration, the B-17 had gone from five rifle-caliber machine guns to ten .50 caliber machine guns.
The first version used in Europe in large numbers was the B-17F, which replaced the original clear nose with a one-piece Plexiglass nose cone. When the Fortresses went into combat in Europe and the Pacific, one more problem was identified: The bomber was vulnerable to attack from the front.
This problem was taken to Ordnance, then to Boeing, and the solution was decided: "Put more guns on it." This solution had already been tested to the maximum with the experimental YB-40, which added a second top turret, doubled the waist guns, and added a Perry remote-control turret under the nose cone, a fitting that was aptly called a "chin turret." The only problem the YB-40 had was that it was too heavy, and couldn't keep up with the regular Fortresses. But the Army, in its infinite wisdom, realized that they still had an "add more guns" solution in the Perry chin turret, which was added to the final form of the B-17, the B-17G.
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Fond as military people are of the "just add more guns" principle, there was another aspect that made the Forts better able to survive their sorties, and that was formation flying.
Despite the impressive concentration of firepower, an individual bomber remained highly exposed, especially during its run-in to the target, when it needed to fly straight and level.
The combat box was therefore soon developed to provide mutual protection, with interlocking arcs of fire provided by bombers flying in formation and staggered at different levels. This presented Luftwaffe fighters with a bigger problem and helped ensure that bombs were delivered close to the chosen target. This latter point was especially important bearing in mind the high altitudes from which these raids were typically flown. However, these tactics also required the bombers to stay in rigid formation if it was to be successful — counterintuitive when coming under attack from fighters or anti-aircraft fire from the ground.
Ultimately, as formations grew in size, the combat box was refined to become the ‘wing box,’ comprising three staggered 18-plane boxes for a total of 54 bombers. This was especially challenging for crews, with closely packed bombers running into each other’s turbulence and with a risk of bombs from a higher stack hitting aircraft flying below. When it worked, however, the wing box provided roughly 700 defensive machine guns that could be brought to bear on fighter opposition.
So, while this is technically a tactical deployment, the answer is still, "Add more guns." That this was done by adding more airplanes and having them fly in overlapping formations that provided a .50 caliber shield that German and Japanese fighters had a hard time penetrating doesn't detract from that fundamental principle.
Even so, the B-17 crews suffered terrible losses. The B-17 was heavily armed but slow, and the Germans in particular were creative in finding new ways to deal with the bomber streams, including jet- and rocket-propelled fighters. Then, early in 1944, everything changed with the advent of the Rolls-Royce Merlin (built under license by Packard) engined P-51 Mustang fighter, which was not only faster, better armed, and more maneuverable than most fighters of its time but also had enough range to escort the bombers to their targets and home again.
It must also be noted that the Army Air Corps and the later Army Air Forces were big on daylight precision bombing, and in this, the B-17 excelled; every bomb ever dropped from a B-17 hit the ground, making for a 100 percent success rate.
The B-17 was a great piece of American military hardware. Along with the B-24 Liberator, the B-17 pretty much defined the doctrine of strategic bombing. The Fort was handsome, tough, could soak up an amazing amount of damage, and even badly shot up, it would still get its crew home safely. It was one of the greatest examples of the wisdom of having bigger and more guns, as well as a great capability for solving problems with the suitable application of high explosives. In both major theaters of the Second World War, the B-17 and its crews earned their place among great moments in military history.
