The Sixth War patrol

    Departing Pearl Harbor for Guam  on 13 March 1945, the boat began her sixth war patrol. She arrived at the Marianna base on 25 March 1945, and three days of specialized training was accomplished. At The Pearl Harbor Submarine Base the boat was outfitted with a new top-secret anti-submarine mine-detecting system called the Frequency Modulated Sonar (FMS) System. CREVALLE completed training on this new sonar under the direction of personnel from Admiral Thomas Lockwood, Commander Submarine Pacific (COMSUBPAC).

    CREVALLE got underway on 28 March 1945, Commander Everett Steinmetz , as her Captain. (Post WWII Commander Steinmetz was the Skipper of a Captured German U-Boat that was in the service of the US Navy ). CREVALLE was ordered to a regular shooting patrol along the East China coast via  Nansei Shoto Island .

The Sixth War Patrol Sailing List:

   During the voyage a four-hour diversion was made in order to perform life guard duty for a B-29 strike on the Island of Honshu, Japan but her services were not necessary as no planes had to ditch in her area. The boat was further ordered to join USS SEAHORSE (SS-304)  and later USS BONEFISH (SS-223)  in an informal wolf pack in which SEAHORSE was designated wolf pack commander.

    The period of 6 to 8 April 1945, was spent first in attempting to intercept the Japanese task force led by the Super Battleship YAMATO and later after it was sunk, by the Seventh Fleet, to search for her survivors. Though both enemy and friendly aircraft contacts were numerous during this period, no contact with the crippled enemy fleet or any of its survivors was ascertained.

    On 9 April 1945, while submerged,  a trawler with a sub chaser as an escort was sighted. A decision was made to attack on the surface with the deck guns and a spirited gun duel commenced and it was soon discovered that the trawler had as much gun power as CREVALLE. With numerous shells falling too close for comfort, CREVALLE dived and torpedoed the sub-chaser, which was now attempting to deliver a depth charge attack. The depth charging terminated abruptly with the downing of the escort and the remaining set of propellers (screws) of the trawler were heard on sonar fading rapidly out of range.

    Shortly after surfacing on the night of 10 April 1945 contact was gained with two more targets. Commencing an attack, three torpedoes were fired at one of the contacts. Two fish struck hard at the vessel sinking a 1,000-ton minelayer. High-speed evasion was performed on the surface to the accompaniment of a few wild and angry shots from the rapidly sinking vessel

    The following evening a torpedo attack was launched on two minor combatant vessels determined to be patrol craft boats. Three bow torpedoes were fired but no hits resulted and evasion on the surface by CREVALLE was unimpeded. A torpedo attack on two pickets boats on 16 April 1945. One was sunk and in sinking it came down practically on top of the boat. Upon surfacing that night, a large crude grapple hook was found on deck along with some Japanese metal life rails and pieces of zinc. In addition, one of the rungs on #1 periscope shear ladder was sawed in two by the wire cable attached to the grapple.

    The period of 23-26 April 1945 was spent in conducting another special mission in the area of the Nishi Suido Straits of Japan. CREVALLE followed after USS SPADEFISH (SS-411)  and SEAHORSE in locating and charting Minefields in the Tsushima Straits between Korea and the home island of Kyushu Japan.  This was accomplished by using the new Frequency Modulated Sonar (FMS) System. With the results obtained from these three ships, a fairly accurate plot of the southern limits of the Japanese home island minefields ensured a tentative starting time for what was to be called Operation Barney a daring penetration of the inland sea of Japan.

    How accurate were the plots made by these three submarines? How meticulous were the plots of other submarine reconnaissance of minefields, strung along the border of the East China Sea from Kyushu to Formosa Island . How precise was the sub's positioning of the mines that were just dropped in clumps in the shallow Yellow and East China Seas? It was not known until after the war when reports from the minesweepers that cleared the area became available. One Lieutenant, stated: "We certainly had to hand it to the submariners who charted those fields. In clearing them out, all we had to do was to use their charts and we knew exactly where to put our sweeps in the water. The mine detection and navigation of those boats were amazingly factual".

    CREVALLE arrived back at Guam on 3 May 1945, where she was refitted by Submarine Division 161 relief crews, and the submarine tender USS PROTEUS (AS-19). This war patrol lasted for 52 days and the Force Commander credited CREVALLE with sinking 1,250 tons of enemy shipping and damaging 167 tons by gunfire. Credit was also given for a successfully completed special mission. The commanding officer, Commander Everett H. Steinmetz, USN, was awarded the Navy Cross.

The entire patrol was characterized by numerous contacts with small shallow-draft anti-submarine groups and radar equipped Japanese planes. The only really large ship contact was made on a properly marked hospital vessel and she was allowed to pass unmolested.