During World War I, tactics that were used successfully in previous wars, such as marching lines of infantry and charging cavalry, were rendered useless by artillery and heavy machine guns. With such huge firepower available, masses of infantry soldiers attempting to charge across a battlefield were practically committing suicide. This forced a change in the infantry tactics and soldiers now dug deep trenches across the battlefield and fought from inside them. New tactics were needed to fight in the trenches. For instance, battles inside trenches were fought at very short ranges because trenches were narrow and twisted. Also, since trenches often contained more enemy soldiers defending it than the attackers, it was necessary to clear the trench before the defenders could mount a counter-attack. What was needed was a small caliber weapon with a high rate of fire, but small enough to be used in narrow trenches and light enough to be carried by a single infantry man.
Heavy machine guns had a high rate of fire, but were heavy, required multiple people to move them and needed a good amount of room to operate. Besides, the range of a heavy machine gun did not matter much inside a trench. Pistols and revolvers were small and light, but didn't have a high enough rate of fire or enough ammunition capacity. Rifles were also light compared to heavy machine guns, but were longer (and heavier) than pistols and revolvers and harder to use inside narrow trenches. They also didn't have a high rate of fire or high capacity and used larger cartridges which were unnecessary in narrow trenches.
In 1915, the German authorities attempted to modify existing semi-automatic pistols, the Luger and the Mauser C96, to use larger magazines and fire in automatic mode. However, these efforts were not successful because the pistols were so light that it was hard to aim them when firing in automatic mode. The German Rifle Commission determined that a new class of weapon was required, one that could fire pistol ammunition, but was designed to fire in fully automatic mode from the very beginning.
The design team led by Theodor Bergmann of Bergmann Waffenfabrik started working on a new design to fulfill this requirement. One of the members of the small design team was a talented designer named Hugo Schmeisser. The design they came up with was adopted in the German military in 1918 and was named the Maschinenpistole 18/I or MP 18.1. No one really seems to know what the "I" designation is, but its successor was named the MP 28/II.
The MP 18/I submachine gun. Click on the image to enlarge.
Image licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license by Edmond Huet.
The MP 18 was made using high quality components and designed to use 9x19 mm. Parabellum cartridges, the same as that used by the Luger pistol. The receiver was machined from a thick tube, unlike later submachine gun models which used much thinner tubes. The bolt was also machined from a single block of steel. It was designed as an open bolt blowback weapon, a feature that was copied by practically every submachine gun designed after it, until about 1970 or so. Schmeisser had already designed several blowback pistols for Bergmann Waffenfabrik, so he adopted the same principle for a larger weapon system. Since adding a high capacity magazine to a pistol made it cumbersome and hard to control in automatic firing modes, he designed the new weapon with a traditional-style wooden body, much like a rifle, so that it would be easier to handle. A barrel shroud was added around the barrel, to counter the overheating of the barrel when fired in full automatic mode. The magazine feed was offset to the left of the receiver and the charging handle was located on the right. The weapon was only designed to fire in automatic mode, but since it had a rate of fire of around 500 rounds per minute, it was possible to fire single shots by pulling and releasing the trigger rapidly.
Interestingly, the early design for the MP 18 used a 20-round box magazine, but the German military insisted that the new weapon use a 32-round "snail" drum magazine (the TM 08 magazine), which was originally designed for the Luger pistol.
A TM 08 snail drum magazine. Click on the image to enlarge.
Image licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license by Edmond Huet.
The snail drum magazine is not a true drum magazine, but is essentially a box magazine folded into a spiral shape. The cartridges are arranged inside it in a spiral pattern and a special loading tool is required to load it. The magazines used with the MP 18 needed to have a special sleeve to prevent the magazine from being inserted too far into the weapon. This snail drum magazine was heavy, awkward and hard to load and was one of the weaknesses of the MP 18.
Nevertheless, the MP 18 was adopted by the German army in early 1918 and about 5,000 (or 10,000) were manufactured. Even though they were not used for very long, these weapons proved to be very useful in trench warfare. In fact, when World War I ended, the treaty of Versailles explicitly forbade Germany from manufacturing any submachine guns. The 32-round snail drum magazine was also prohibited from being manufactured by the same treaty. However, Bergmann Waffenfabrik continued to manufacture this weapon in secret until about 1920 and a total of about 35,000 weapons were made. After that, Bergmann sold the design and manufacturing license to SIG of Switzerland, who started to sell it as the SIG Bergmann 1920. The Swiss produced different versions that could fire 9x19 mm. cartridges (the same as the Luger) and the 7.63x25 mm. cartridges (the same as the Mauser C96). It continued to be used by police forces in the Weimar republic, as well as China, France, Finland etc. Hugo Schmeisser modified the design to use the 20 round box magazine that he'd originally designed for it, and later, 40 and 50 round box magazines were also made for it. In 1928, he modified the design to have a selector switch and this new model was called the MP 28/II.
The MP 18 was the world's first submachine gun (technically, the Italian Villar-Perosa from 1915 was also an automatic weapon firing pistol caliber ammunition, but it was originally designed to be used as a mounted weapon in aircraft). It was influential in the designs of submachine guns that followed it. For instance, it was the MP 18 that inspired the Finns to invent their own Suomi KP/-31 submachine gun that we saw in our previous post. The British designed their Lanchester submachine gun based on the MP 28 and even made it use the same magazines as the MP 18 and MP 28. The later Sten gun could also use the MP 18 box magazines. Practically every submachine gun designed after it until about 1970, used a blowback system of operation and fired from an open bolt.
While the MP 18 was an influential design, it was also heavy and somewhat expensive to produce because key parts were machined from solid steel blocks. Later submachine guns were designed to be manufactured much more quickly and at lower costs, by using stamping and spot welding techniques.
Incidentally, it is ironic that Hugo Schmeisser's name is not associated much with the MP 18, a weapon where he made very significant contributions to the design. However, his name is popularly associated with the MP 40, a weapon that he made very little contribution to. It turned out that the German War Office mandated that the MP 40 use a magazine design that he'd actually patented for the MP 18 and MP 28 and therefore, his name somehow got associated with the MP 40 and it is referred to as the "Schmeisser submachine gun" in many countries.
