March 5, 1970

Treaty on the Non-Proliferation of Nuclear Weapons

Nuclear Non-Proliferation Treaty enters into force

One American ratification instrument had to travel through three diplomatic channels — Washington, London and Moscow — all on the same day.

The threshold cleared

On 5 March 1970 the Treaty on the Non-Proliferation of Nuclear Weapons entered into force. Article IX required deposits from the three depositary governments — the United States, United Kingdom and Soviet Union — plus at least 40 other signatory states.

The United States deposited its ratification in London, Moscow and Washington that day, and the Soviet Union completed its deposits the same day. Britain had deposited in 1968. A contemporary Congressional account reports 47 ratifying nations.

11:23 a.m., Washington

At a State Department ceremony, President Richard Nixon announced that its completion had put the treaty into force and made it United States law.

That was the moment a negotiated text became binding on its original parties.

A 180-day clock starts

Entry into force began the timetable under Article III: non-nuclear-weapon parties had 180 days to begin negotiating safeguards agreements with the International Atomic Energy Agency.

Two of today's treaty-recognized nuclear-weapon states were not parties that day. France and the People's Republic of China acceded only in 1992.

Sources

Researched 23 Aug 2026 6 sources 3 audit passes

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

What the sources leave uncertain

Sources sometimes count the entry-into-force states differently because each instrument could be deposited separately in London, Moscow, and Washington. The treaty’s legal threshold was 43 states; a contemporary Congressional account reports 47 ratifying nations by March 5.