WASHINGTON, June 4 (UP)--The daring exploit of an American submarine which sneaked at night into a harbor jammed with Japanese ships, surfaced under the muzzles of enemy guns, torpedoed vessels all around it and then got away in a miraculous exhibition of broken field running, was revealed today by the navy.

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It was a thriller such as usually is encountered in boys' war books but it sounds too incredible to really happen.  But this episode was real enough to have earned Cmdr. Eugene B. Fluckey of the submarine Barb the Medal of Honor and his entire crew the Presidential Unit Citation.

  Cmdr. Fluckey long had suspected that a certain harbor concealed a haven hiding a large number of Japanese tankers, munitions ships and warships.   On a dark night when visibility was poor, Cmdr. Fluckey found the target.

  The navy said Cmdr. Fluckey took his ship on what appeared to be a hopeless mission because the anchored convoy he was after was hidden behind a protecting screen of escorts concentrated on every logical approach.

  The water was so shallow that the 1,500 ton Barb was forced to remain on the surface during her approach and for at least an hour afterward.

  Faced with one of the best targets he had ever had, Cmdr. Fluckey decided to attack despite the odds.  The escape involved a fight through uncharted water filled with mines and rocks and packed with fishing junks.

  But Cmdr. Fluckey figured that the Japanese escort vessels would hesitate to make a run through the rocks and that they would find the junks a handicap.

  The Barb moved inside the screen of Japanese escorts and let go with all the torpedoes she could fire in the time available.  Then Cmdr. Fluckey ordered full right rudder and moved toward the rocks.

  From the bridge Cmdr. Fluckey saw the Japanese ships erupting like a nest of volcanoes.  Columns of fire leaped from several vessels.   The first target settled in the water and the others burned.

  Only the Japanese know how many went down.  Cmdr. Fluckey had no time to count.

  The Japanese escorts moved up in hot pursuit, tossing a hail of shells at the Barb.  Many were close, but all missed.  The junks confused the enemy and several became targets for Japanese guns instead of the Barb.

  The sub skinned by the rocks and reached open water at dawn.  A Japanese plane spotted her and she submerged for the first time since she sighted the target.