When Mauno Koivisto was elected president of Finland in 1982, Leonid Brezhnev was still in the Kremlin and Ronald Reagan had been the U.S. president for a year. Relations between the superpowers were at low ebb, and there seemed little prospect of improvement. A "Treaty on Friendship, Cooperation and Mutual Assistance" with the USSR had been signed by a weakened Finland in 1948, and its military provisions led to talk of "Finlandization." The Soviets would not accept the concept of Finnish neutrality, to which the Finns adhered strongly. When Koivisto left office in 1994, the Soviet Union...