The Type XXI could run submerged at 17 knots (31 km/h), 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.[citation needed] 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.