Why Russia’s Type 49 ‘Burp Gun’ Was a Communist’s Weapon of Choice Submachine guns began to appear near the end of World War I to help soldiers clear out trenches in brutal short-range assaults. Here's What You Need to Remember: Communist troops would infiltrate close to UN positions under the cover of night—then surged forward in a human wave only visible at short range. While many attackers fell to defensive fire, once the shock troops flooded into the UN outposts, their burp guns hosed out greater volumes of firepower. Submachine guns began to appear near the end of World War I to help soldiers clear out trenches in brutal short-range assaults. These short barreled, highly portable automatic weapons usually employed the simple blowback principle in which the gasses expelled by a low-powered pistol cartridge both propelled the round out of the barrel and pushed back the weapon’s bolt, allowing a new round to pop up into the chamber to be fired once the bolt sprang back into place.