During the last year of World War II, the Japanese Navy turned Misaki Marine Station, where Katsuma Dan worked, into a submarine base. When the U.S. Navy took over the base, Dan wanted to let them know its significance. In August, 1945, he left a poster pinned to the door, explaining the purpose of the station:

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A letter from L. S. Parks accompanied notes sent back to Woods Hole in October, 1945:

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In 1946, Katsuma Dan sent a letter to Donald Costello giving a short account of the war years and explaining the events behind the “Last One to Go” poster:

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