German searchlights of the Second World War were used to detect and track enemy aircraft at night. They were used in three main sizes, 60, 150 and 200 centimetres. After the end of the First World War, German development of searchlights was effectively stopped by the Treaty of Versailles, it resumed in 1927. At the outset of the war, searchlights were combined with acoustic direction-finders, with the direction-finders guiding the searchlights to the right part of the sky, where they swept until they found the target. Later in the war, the searchlights were radar-directed. The searchlights were based around extremely high-powered Carbon Arc lamps.