originally these wires were designed as \"jumping wires \"and used as anti-submarine net deflectors. If a U-boat ran into a net it had sharp cutters on top of the bow and below it in order to cut through the net ,then these wires would deflect the open net over the surface of the boats hull so as not to get snagged on the conning tower ,hand rails etc. The second use for these wires was to act as an antenna for the high frequency radio. The single front wire from bow to conning tower acted as the transmitting antenna and the two aft wires were the receiving antenna. Most WWI German U-boats used these wires as a net deflector only as they had tall,folding radio antenna masts. In WWII U-boats used these wires more as radio antennas as the net deflector proved to be impractical as nets were not used to the degree that they had been in WWI. Later in WWII as more U-boats were equiped with the telescopic rod antenna ( that tall bulge along the port side of late war conning towers) this replaced the net deflector jumper wires as the boats main radio antenna.