During World War II, when all commercial ships were taken over by central governments and repurposed by the military, one set of ships were treated differently — the "exchange ships."

Many foreigners, including diplomats, journalists and scholars, were stranded in "enemy" nations when war broke out, and it was the responsibility of the exchange ships to take them back to their home countries. Since the war meant a breakdown in diplomatic relations between enemy nations, politically neutral countries such as Switzerland and Sweden offered their ports to allow the ships to retrieve their nationals.

On show are photographs of those exchange ships, as well as exhibits detailing how Japan's commercial ships ended up subject to extreme militarization; till Dec. 9.

NYK Maritime Museum; (045) 211-1923; 3-9, Kaigan-dori, Yokohama, Kanagawa; Bashamichi Station, Minato Mirai Line. 10:00 a.m.-5:00 p.m. ¥400. Closed Mon. www.nyk.com/rekishi.