By 1944, the outcome of World War II was no longer in doubt. The allies were to win it. The whole question was how long Germany, Japan and their remaining satellites would be able to prolong the conflict. In 1944, the Red Army carried out one of its most successful operations in history; the German Army Group Center was defeated by the blows of the Bagration. In June of the same year, troops from the United States, Great Britain and Canada landed on the beaches of Normandy, opening the Second Front in Europe, and the territory controlled by Japanese troops in the Pacific was rapidly shrinking.
The American military increasingly thought about a possible invasion of Japan itself. It was assumed that on its own soil, the Japanese imperial army would show very fierce resistance on the prepared lines of defense. As a means of destroying the long-term fortifications of the Japanese, a mortar of a very large caliber - 914 mm (or 36 inches) - was proposed. According to this indicator, the American project, which was jokingly called Little David (Little David), surpassed the German super-large-caliber artillery systems known all over the world, both Karla (600 mm) and Douro (807 mm).
The unique American mortar, which still holds the record for the largest caliber among all modern artillery, was created on the basis of an experimental system designed to test large-caliber aerial bombs. The mortar was distinguished by the fact that, with a caliber larger than that of the German giants of the Second World War, it was more compact than theirs, however, its firing range was quite modest. Structurally, an unusual artillery mount was a barrel slightly more than 7 meters long and weighing more than 36 tons and a stationary base in the form of a box, which had to be buried in the ground, weighing about 46 tons. The two main parts of the mortar were transported by two tank transporters.
During World War II, the American army often used the retired large-caliber naval gun barrels to test air bombs. The tests were carried out using relatively small powder charges, which were enough to send a bomb over a distance of several hundred yards. Such systems were used by the Americans because during the usual dropping of bombs from an aircraft, much depended on the change in weather and the ability of the bomber crew to accurately fulfill all test conditions. With the increase in the caliber of bombs, 9- and 12-inch gun barrels were no longer suitable for these purposes. Therefore, in the United States, it was decided to create a device that received the designation Bomb Testing Device T1.
This device has proven itself very well, and the experience gained formed the basis for the idea of using it as an artillery weapon. It was planned to use it against fortified enemy targets, mainly well-defended fortifications. The Americans were very afraid to meet with the defense in depth of the Japanese islands with a lot of fortifications and bunkers. The project was launched in March 1944, the same year, but already in October, test firing began. The US military expected to have at its disposal a more powerful weapon than the 16-inch cannons that were on the Iowa-class battleships. During the battle for Iwo Jima in February-March 1945, the 1200-kg shells of these guns showed their insufficient effectiveness against the Japanese bunkers located on the island.
Externally created in the USA, the 914-mm mortar Little David was a muzzle-loading mortar with a rifled barrel, which rested on a large steel box (5500x3360x3000 mm) weighing more than 46 tons, dug into a deep hole. The steel box, which was the base of the mortar, housed a vertical guidance mechanism, as well as six hydraulic jacks designed to install and extract the barrel, which weighed more than 36 tons. The barrel of the mortar was lowered and raised using a "quadrant" with a drive from the breech, the width of the box made it possible to aim the mortar horizontally. The mortar had no knurl, the hydraulic recoil brake was concentric. A pump was used to return the barrel to its original position after the shot.
Especially for this mortar, a unique T1-HE projectile was created with a long tapered nose and cutouts that had to match the rifling of the barrel for reliable obturation. The mass of the projectile was 1,678 kg (3,700 lb), of which 726 kg (1,600 lb) was the mass of the explosive. Mortar could send such a projectile at a distance of 8687 meters (9500 yards). Loading was carried out from a muzzle, a separate cap. At zero elevation, the T1-HE projectile was fed into the barrel using a crane, after which it moved a certain distance, then the mortar barrel was raised, and further loading was carried out under the influence of gravity. A primer-igniter was inserted into the socket, which was located in the breech of the barrel. The mass of the full charge was 160 kg, caps for 18 and 62 kg were used. It was believed that the destructive effect of such a projectile would be sufficient to destroy any targets. The funnel, which remained at the site of the rupture, reached 12 meters in diameter and 4 meters in depth.
The mortar was created in a single copy and never left the location of the Aberdeen Proving Grounds, which means it did not take part in the hostilities either. The tests of the artillery installation dragged on, the Second World War ended, and the invasion of the Japanese islands was never required. Therefore, work on the mortar was frozen at the stage of finishing tests. At the same time, the main disadvantages of the 914-mm artillery system, which included a small firing range (less than 9 kilometers) and insufficient accuracy, were never eliminated. The project was completely closed in 1946.
The American military was not encouraged by the 12 hours it took to deploy mortars and equip positions. In fairness, it should be noted that the German super-heavy 800-mm railway gun "Dora" was transported by 25 special railway platforms, and the process of bringing the gun into combat readiness with the arrangement of a firing position took weeks. Near Sevastopol, it took the Germans 4 weeks to equip the position, despite the fact that more than three thousand people, including prisoners of war, took part in the work. In this regard, the American Little David mortar was much more mobile, and it was much easier to deploy it. For its transportation, two powerful tank transporters M25 Tank Transporter (G160) with a 6x6 wheel arrangement were used. One transporter transported the barrel part, the second - the box-base. Thus, the mortar was much more mobile than the railway guns. In addition to the 914-mm mortar itself, the unit included a bulldozer, a crane and a bucket excavator, which were supposed to participate in equipping an artillery position.
After the closure of the project, the Little David mortar became a museum piece and is today presented in an extensive exhibition at the Aberdeen Artillery and Technical Museum. Here everyone can see the barrel and the box-base of the mortar, which rest on the wheels of the transporters, as well as one of the unique shells. The video footage of the tests of this artillery "monster" which has survived to this day is also of interest.
The performance characteristics of the Little David mortar:
Caliber - 914 mm.
The total weight is more than 82 tons (including the base).
Length - 8534 mm (barrel).
Barrel length - 7120 mm (L / 7, 8).
Elevation angle - from + 45 ° to + 65 °
The horizontal guidance angle is 26 °.
Projectile weight - 1678 kg.
The mass of the explosive in the projectile is 736 kg.
The initial speed of the projectile is 381 m / s.
The maximum firing range is 8687 m.
Deployment time is 12 hours.