The development of the Type XXIII was given very high priority. To reduce development time, Dr. Walter designed the new boat based on the previous Type XXII prototype. By June, 1943, the initial design was ready and construction began in parallel at several shipyards in Germany, France, Italy and German occupied USSR. The Type XXIII had an all welded hull design, and was the first submarine in the world to use a single hull design. For the power plant, the Type XXIII used the MWM RS-348 diesel engine, which was already in use as a diesel generator aboard the Type IXDs. The electric motor was the AEG GU 4463/8, which was a simplified version of the electric motors employed on the Type VIIs. Handling wise, the Type XXIII proved to be an excellent boat, which was highly maneuverable both on the surface and underwater. Crash dive time was a quick 9 seconds. Construction of this advanced submarine faced a logistical nightmare. Many disruptions were caused by Allied land advances, constant aerial bombings, material and manpower shortages. Of the 280 submarines ordered, only 61 had entered service.