target offered to the torpedoes, but at the same time be able to aggressively engage the firer. This was the tactic advocated by critics of Jellicoe's actions at Jutland, his caution at turning away from the torpedoes being seen as the reason the Germans escaped. The use of multiple torpedoes to engage single targets depletes torpedo supplies and greatly reduces a submarine's combat endurance. Endurance can be improved by ensuring a target can be effectively engaged by a single torpedo, which gave rise to the guided torpedo. Pattern running In World War II the Germans introduced programmable pattern-running torpedoes, which would run a predetermined pattern until they either ran out of fuel or hit something. The earlier version, FaT, ran out after launch in a straight line, and then weaved backward and forwards parallel to that initial course, whilst the more advanced LuT could transit to a different angle after launch, and then enter a more complex weaving pattern. Radio and wire guidance Though Luppis' original design had been rope-guided, torpedoes were not wire-guided until the 1960s. During the First World War the U.S. Navy evaluated a radio controlled torpedo launched from a surface ship called the Hammond Torpedo. A later version tested in the 1930s was claimed to have an effective range of . Modern torpedoes use an umbilical wire, which nowadays allows the computer processing power of the submarine or ship to be used. Torpedoes such as the U.S. Mark 48 can operate in a variety of modes, increasing tactical flexibility. Homing Homing "fire and forget" torpedoes can use passive or active guidance or a combination of both. Passive acoustic torpedoes home in on emissions from a target. Active acoustic torpedoes home in on the reflection of a signal, or "ping", from the torpedo or its parent vehicle; this has the disadvantage of giving away the presence of the torpedo. In semi-active mode, a torpedo can be fired to the last known position or calculated position of a target, which is then acoustically illuminated ("pinged") once the torpedo is within attack range. Later in the Second World War torpedoes were given acoustic (homing) guidance systems, with the American Mark 24 mine and Mark 27 torpedo and the German G7es torpedo. Pattern-following and wake homing torpedoes were also developed. Acoustic homing formed the basis for torpedo guidance after the Second World War. The homing systems for torpedoes are generally