A recently declassified U.S. document confirms that Japan gave the United States its official consent to bring nuclear weapons to Okinawa shortly before the 1969 bilateral accord that led to the occupied island's 1972 reversion to Japanese rule.

The finding is significant because it shows Japan's leaders officially agreed during the Cold War to violate the Three Non-Nuclear Principles set out by Prime Minister Eisuke Sato in 1967 while publicly telling the rest of Japan that nuclear weapons would not be brought to the prefecture.

The principles, which helped Sato win the Nobel Peace Prize in 1974, state that Japan will not possess, produce or allow nuclear weapons on its territory. They have been the foundation of Japan's nuclear arms policy ever since.