Wakkanai – port on the island of Hokkaido, the northernmost city in Japan. The city is located on the shore of the Sea of Okhotsk La Perouse Strait, which separates the island of Hokkaido, Sakhalin.
Wakkanai was originally home to an Ainu population. The first Japanese settlement was established in 1685.
During WW II: The Imperial Japanese Navy used the harbor and port as a submarine base. Wakkanai, was far enough north to be out of the range of American heavy bombers and was safe from air attack. Until the early-mid 60’s, the northern portion of the harbor remained divided by concrete sub-mooring pens.
The large breakwater structure (which still exists) was actually a sub-repair facility. At the shore end there was a huge winching mechanism capable of hauling subs up into the partially enclosed structure where they could be worked on while completely out of the water. Built into the hills above the city there were several reinforced concrete bunker-type caves where (anecdotally) they were used either to store ammunition and armament, or as air raid shelters for the civilian populace.
History would suggest the former use, rather than the latter. During a re-build / renovation of the harbor sometime during the 60’s or 70’s the harbor was cleared of the concrete pens and the machinery was removed from the breakwater structure which was reconfigured.