Submarine

At the beginning of the 20th century, the submarine equipment was gradually improved and its performance was gradually improved. Submarines with certain combat capabilities appeared. These submarines adopt double hull, with good airworthiness, displacement of hundreds of tons, and use diesel-electric dual propulsion system. The speed on the surface is about 10-15 knots, and the underwater speed is 6-8 knots, and the endurance is significantly improved; The weapons mainly include artillery, torpedo and torpedo. Before the First World War, the major naval countries had more than 260 submarines, which became one of the important combat forces of the Navy.

At the beginning of the First World War, submarines were used in combat. On September 22, 1914, the German U-9 submarine sank three British cruisers in succession within more than one hour, fully demonstrating the submarine's combat power. During the war, submarines from all countries sank a total of 192 combat ships. The use of submarines to attack the transport merchant ships on the ocean traffic line has achieved more remarkable results. Submarines from various countries have sunk more than 5000 merchant ships, up to 14 million tons. About 13 million tons of merchant ships were sunk by German submarines. At the same time, anti-submarine warfare began to receive attention. During the war, 265 submarines were sunk, of which Germany lost more than 200.

After the First World War, the major naval countries paid more attention to the construction and development of submarines. The number and types of submarines are increasing. By the eve of the Second World War, there were more than 600 submarines. During the Second World War, the tactical and technical performance of submarines has been greatly improved. The displacement has increased to more than 2000 tons, the diving depth is 100~200 meters, the maximum underwater speed is 7~10 knots, the surface speed is 16~20 knots, the endurance is more than 10000 nautical miles, the self-supporting force is 1~2 months, 6~10 torpedo launch tubes are installed, which can carry more than 20 torpedoes, and 1~2 guns are installed. At the end of the war, submarines were equipped with radar, radar reconnaissance instrument and homing torpedo, and German submarines were also equipped with breather pipes for diesel engine underwater work. Submarine combat activities are almost all over the oceans, and are responsible for attacking transport ships, surface combat ships and reconnaissance, transportation, anti-submarine, mine laying and transportation of reconnaissance, blasting personnel landing and other tasks. More than 5000 transport ships (more than 20 million tons) were sunk, and more than 300 large and medium-sized surface ships were sunk. Anti-submarine forces and weapons have also been greatly strengthened and developed in the war, with more than 1100 submarines sunk.