Following the Second World War, it was recognized that there was a need to improve the submerged speed, maneuverability, and endurance of our submarine force.  The Greater Underwater Propulsion Power Program was instigated.  Like all programs in the military, some sort of "name" needed to be applied that would attract and hold attention.  Since GUPPP didn't sound quite right, the third P was dropped and a Y added.  Thus the word GUPPY, which had a far better ring to it since it did in fact sound more like a fish.   At this time all submarines were named after undersea life.

    Jim Christley has conducted extensive research on the GUPPY program and most of the information contained here is the result of his tireless efforts.  Jim writes that after the war the Navy obtained two German Type XXI boats.  These were studied and tested extensively. 

   A history of events leading up to the Guppy conversions indicates the following:  According to Christley's article, "Why is there a "Y" in GUPPY?" the two German Boats studied were the U-2513 and U-3008.  The lessons learned:  increase the battery capacity, streamline the boat's structure, add a snorkel, and add a better fire control sytem.  A new design was created called the TANG Class.  The new boat was so much better that it made the existing fleet boat obsolete.  The new boat was expensive.  The Navy had to find a way to upgrade the existing fleet boats to match the TANG class's ability.  (See photo of U2513 below) 

    Included in this site is a section for each of the Guppy classes.  You can check back on the opening page for a link to each class.  There were seven major conversion types:  The Guppy I, Guppy IA, Guppy IB, Guppy II, Guppy IIA, Guppy III, and the Fleet Snorkel.

    The boats that were converted to Guppys were "rode hard."  They had to support ASW training with US and NATO Task Groups, run barrier patrols in the GIUK GAP (Greenland, Iceland, UK, Gap, that narrow passage through which the Soviet submairnes would have to deploy to threaten the Atlantic sea lanes.)  Such operations took place from the mid 1940's to the present day.  "The US and allied Navies kept watch on the Soviet Naval entrance and exit points to track the deployment of the Soviet Fleet.  The Med runs kept count of the Soveit boats training in the Dardenelles.  The Brits, Danes, Dutch, and Norwegians watch the North Sea and Baltic exit points.

   In the Pacific, boats from Pearl Harbor, San Diego and Yokosuka watched the exit points from the North Pacific ports such as Vladivostok.  The US and other NATO boats watch the Kola Peninsula.  Along with the watch on the Soviets, there was the tracking of operations and testing the abilities of all Warsaw Pact Navies.  These operations and training exercises took place in what would become standard deployments.  A WesPac (deployment) took a boat from its home port at Pearl Harbor or San Diego and attached it to the Seventh Fleet in Yokosuka, Japan for six to seven months of operations.  A med run took a New London, Norfolk, Charleston or Key West boat and attached it to the Sixth Fleet in the Med for six months.  Each of these meant a long ocean transit of ten to seventeen days in Atlantic storms and Pacifc typhoons.  There were the UNITAS runs around South America, a trip that could last up to six months.  Then there were the Northern Runs! 

   Operations on the Northern run, in Atlantic operations, and on WesPac deployments frequently found the Guppys in extremely rough weather.  Boats on Northern runs operated in state five to six and higher seas constantly.  Atlantic storms and typhoons in the Pacific found the boats in those areas frequently battling extremely foul weather as they fulfilled their missions.  "The Guppy bow dug deeply into the waves and the step sail was little protection.  Control during snorkeling was difficult at  best and sometimes impossible.  The snorkel induction, topped by the head valve, had to be kept out of the water.  If it ducked to the surface or below, or a wave hit it, it would automatically slam shut.  The diesel engines would keep running for a short time removing some sixteen thousand cubic feet of air from the boat's internal atmosphere per minute per engine.  It would take from ten to thirty seconds for the engines to draw enough vacuum in the boat to shut down automatically after the snorkel induction head valve shut depending on whether the boat was running on one or two engines.  This occurred at a vacuum of six inches of mercury below atmosphere.  This equivalent to a 6000-foot altitude.  Sometimes the head valve would shut for five or six seconds then reopen as the snorkel induction again cleared the surface.  The atmospheric pressure would return to normal in the next few seconds, then the head valve would shut as another wave passed.  This cycle would occur over and over for days and days."

   The majority of the information about the operations of the Guppys during the Cold War remains classified to this day.  However, without the conversion from the fleet boats of WWII to the Guppys of the Cold War era, the operations that the Guppys were responsible for would not have been possible.  The success of submarine cold war operaions is directly related to the crews and the Guppy conversions.  These submarines, and their crews, certainly "Held the Line" during the Cold War until the SSNs and SSBNs took over to continue the high tradition of the United States Submarine Service.

    This web site is a tribute to the Guppys.  However, nothing would have been possible without the dedication, professionalism, and courage of the crews who manned them.  These crews, and their boats, continued the legacy from their WWII brothers, and "stood their  ground" until the SSNs and SSBNs assumed their responsibilities.  You will not hear much about that period in our submarine history.   We remain the "Silent Service."