 The boats were unsuccessful, largely because of the professional nature of veteran Allied naval commanders in their construction of convoys and their preparation of escorts.The North Sea proved largely barren, as most shipping was concentrated in the heavily defended English Channel, as so it was nearly a month after leaving Horten Naval Base in Norway that "U-2321" scored her first and only victory, torpedoing the unescorted 1,400 ton steamship .Four days later, "U-2321" was back in port at Kristiansand, where she was still berthed when Germany surrendered on 9 May.