Late in the war, the Germans introduced the "Elektroboot": the Type XXI and short range Type XXIII. The Type XXI could run submerged at , faster than a Type VII at full speed surfaced, and faster than Allied corvettes. Designs were finalised in January 1943 but mass-production of the new types did not start until 1944. By 1945, just five Type XXIII and one Type XXI boats were operational. The Type XXIIIs made nine patrols, sinking five ships in the first five months of 1945; only one combat patrol was carried out by a Type XXI before the war ended, making no contact with the enemy.