The arrest last Friday of a Maritime Self-Defense Force officer on suspicion of spying for Russia raises the puzzling question: How is it that Moscow needed, or seemed to need, military secrets from Japan in the post-Cold War period, particularly at a time when relations between the two nations are improving?

The Metropolitan Police Department and the Kanagawa Prefectural Police arrested Lt. Cmdr. Shigehiro Hagisaki, a member of the Defense Agency's National Institute for Defense Studies, on charges of passing defense secrets to a Russian military attache at the Soviet Embassy here. Investigators say Lt. Cmdr. Hagisaki met the Russian at a Tokyo restaurant approximately 10 times between last September and this August to give him confidential information.

The Self-Defense Forces Law prohibits SDF personnel from disclosing classified information to third parties. Anyone who has leaked such information is liable to a prison term of up to one year or a fine of not more than 30,000 yen. According to police, Lt. Cmdr. Hagisaki has admitted giving the Russian officer an assortment of classified data, including the names and addresses of senior SDF officers. It is not yet known whether the rest of data included more sensitive information.