The Non-Proliferation Treaty enters into force. [see July 1, 1968]
The Soviet nuclear submarine K-8 sinks in the Bay of Biscay, killing 53 crew members.
The main rounds of Strategic Arms Limitation Talks (SALT) open in Vienna.
The United States deploys the first missile with multiple independently targetable reentry vehicles (MIRVs), the Minuteman III.
A large radioactive cloud is released after a 10 kiloton underground test in Nevada. The test, codenamed Baneberry, is part of the nuclear tests in which radioactivity is deliberately vented out from underground. The cloud made its way to Canada.