#375mm

Anti-submarine warfare began soon after the first armed submarines appeared. In WW1, the main weapons were depth charges and mines. Then the first active sonars began to appear, along with a new type of weapon: anti-submarine mortars, with its prime example being the British Hedgehog. These mortars would later be improved into rocket launchers, which had considerably greater range and could launch much larger explosive charges. Bofors would develop one of the first such launchers: the 375 mm M/50 anti-submarine rocket launcher. Adopted by many countries and installed on numerous ships, it revolutionized close-range anti-submarine warfare and is still in use today.