1987 -- December 9: JOINT VERIFICATION EXPERIMENT - During a Washington summit, the United States and the Soviet Union agree to design and conduct a joint verification experiment (JVE) at each other's test sites. The U.S. portion of the JVE is conducted on August 17, 1988, and the Soviet portion on September 14, 1988. U.S. and Soviet scientists, technicians, and observers are present at both experiments.
1987 -- November 9: U.S.-SOVIET NTT TALKS - Based on the Washington ministerial, the Nuclear Testing Talks resume, with the focus on TTBT/PNET verification issues (see July 25, 1986).
1987 -- September 17: WASHINGTON MINISTERIAL - U.S. Secretary of State George Shultz and Soviet Foreign Minister Eduard Shevardnadze announce that "[t]he United States and Soviet sides have agreed to begin before December 1, 1987, full-scale stage-by-stage negotiations which will be conducted in a single forum. In these negotiations, the sides, as the first step, will agree upon effective verification measures which will make it possible to ratify the [TTBT and PNET], and proceed to negotiating further intermediate limitations on nuclear testing leading to the ultimate objective of the complete cessation of nuclear testing as part of an effective disarmament process."
1987 -- February 5: END OF SOVIET MORATORIUM - The Soviet Union announces that, since the United States has not stopped testing, its own moratorium has ended. The Soviets resume nuclear tests on February 26.
1987 -- January 13: VERIFYING NUCLEAR TESTING TREATIES - President Reagan sends a message to the U.S. Senate requesting advice and consent on ratification of the TTBT and PNET, with a reservation that will ensure the treaties do not take effect until they are effectively verifiable.
1985 -- December 5: - COMPREHENSIVE TEST BAN In a letter to President Reagan, General Secretary Gorbachev proposes the resumption of negotiations on a CTB. On December 19, the White House states that: "A comprehensive test ban...is a long-term objective of the United States in the context of achieving broad, deep, and verifiable arms reductions, substantially improved verification capabilities, expanded confidence-building measures, greater balance in conventional forces, and at a time when a nuclear deterrent is no longer as essential an element as currently for international security and stability."
1986 -- July 25: GENEVA TALKS ON NUCLEAR TESTING - As a result of President Reagan's March 14 offer, U.S. and Soviet experts begin the first round of the Nuclear Testing Talks (NTT) in Geneva, Switzerland.
1986 -- May 14: SOVIET MORATORIUM EXTENDED AFTER CHERNOBYL - After the Chernobyl nuclear reactor accident, General Secretary Gorbachev extends the Soviet nuclear testing moratorium through August 6, 1986. It is later extended until the end of the year.
1986 -- March 14: ON-SITE MONITORING OF NUCLEAR TESTS WITH CORRTEX - President Reagan announces a new, specific proposal for on-site monitoring of nuclear tests to strengthen the verification provisions of the TTBT and PNET. The proposal involves a hydrodynamic yield measurement method -- known as CORRTEX -- that Soviet scientists are invited to inspect at the U.S. test site and to monitor during a nuclear weapons test.
1986 -- January 15: SOVIET MORATORIUM EXTENSION - In connection with his three-stage nuclear disarmament plan, General Secretary Gorbachev extends the Soviet testing moratorium for three months beyond its December 31, 1985, expiration date.
1985 -- July 30: SOVIET TEST MORATORIUM - Soviet General Secretary Mikhail Gorbachev announces a nuclear testing moratorium to begin August 6 and last until the end of 1985. He pledges to continue the testing ban beyond December if the United States reciprocates.
1985 -- July 29: MEASURING NUCLEAR TESTS - President Reagan invites Soviet experts to the U.S. test site in Nevada to measure the yield of a U.S. nuclear test with any instrumentation devices they think necessary.
1982 -- July 19: TTBT AND PNET VERIFICATION PROTOCOLS - U.S. President Ronald Reagan determines that the United States will seek to negotiate additional verification protocols to the TTBT and PNET.
1980 -- October 16: LAST ATMOSPHERIC TEST - China conducts the last atmospheric nuclear test to date.
By 1979, the trilateral CTB negotiations are overshadowed by the Strategic Arms Limitation Treaty (SALT II) and, later, by the Soviet invasion of Afghanistan. The trilateral talks recess at the end of the administration of U.S. President Jimmy Carter (1981) and do not resume.
1977 -- October 3: TRILATERAL CTB TALKS - Trilateral talks for a CTB begin in Geneva between the United States, Britain, and the Soviet Union. Over the next three years, progress is made on the draft treaty: The parties agree that the treaty will ban all nuclear weapons tests, suspend PNEs until they can be distinguished from weapons tests, establish an extensive verification regime (including national technical means and seismic monitoring stations), and permit on-site inspections to ensure confidence in the treaty. Differences remain on details of the verification regime, the definition of a "nuclear explosion," and the status of the treaty after its three-year term.
1976 -- May 28: PEACEFUL NUCLEAR EXPLOSIONS TREATY - U.S. President Gerald Ford and Soviet General Secretary Leonid Brezhnev sign the Treaty on Underground Nuclear Explosions for Peaceful Purposes (the Peaceful Nuclear Explosions Treaty), which sets a ceiling of 150 kilotons on such explosions, equal to that established in the TTBT. The treaty provides for verification by national technical means, information exchange, and access to the test site. Pending ratification, both parties pledge not to test above 150 kilotons.
1974 -- July 3: THRESHOLD TEST BAN TREATY - The United States and the Soviet Union sign the Treaty on the Limitation of Underground Nuclear Weapon Tests (the Threshold Test Ban Treaty). The treaty bans underground nuclear weapons tests with a yield exceeding 150 kilotons and obligates the parties to continue negotiations toward a CTB. The treaty provides for verification by national technical means, exchange of data on test site geology, and testing only on national territory at announced sites.
1974 -- May 18INDIAN NUCLEAR TEST - India conducts its only nuclear test to date at an underground test site in the Rajasthan Desert.
1974 -- March/April: RESUMPTION OF DISCUSSIONS ON NUCLEAR TESTING LIMITS - The United States and the Soviet Union resume discussions on nuclear testing limits that lead to the Threshold Test Ban Treaty (TTBT) and the Peaceful Nuclear Explosions Treaty (PNET).
1976 -- May 28: PEACEFUL NUCLEAR EXPLOSIONS TREATY - U.S. President Gerald Ford and Soviet General Secretary Leonid Brezhnev sign the Treaty on Underground Nuclear Explosions for Peaceful Purposes (the Peaceful Nuclear Explosions Treaty), which sets a ceiling of 150 kilotons on such explosions, equal to that established in the TTBT. The treaty provides for verification by national technical means, information exchange, and access to the test site. Pending ratification, both parties pledge not to test above 150 kilotons.
1968 -- July 1: NUCLEAR NON-PROLIFERATION TREATY - The Treaty on the Non-Proliferation of Nuclear Weapons (NPT) is signed by the United States, the Soviet Union, Britain, and 58 other countries. The preamble of the agreement refers explicitly to the CTB and to the "determination expressed by the Parties [to the treaty] to seek to achieve the discontinuance of all test explosions of nuclear weapons for all time." The NPT enters into force March 5, 1970.
1964 -- October 16: FIRST CHINESE NUCLEAR TEST - China explodes its first nuclear weapon at Lop Nor on the Qinghai Plateau.
1963 -- July 15-August 5: LIMITED TEST BAN TREATY - The United States, Britain, and the Soviet Union negotiate and sign on August 5 the Limited Test Ban Treaty (LTBT) outlawing nuclear tests in the atmosphere, in outer space, and underwater. Underground tests are also outlawed if they result in spreading radioactive debris outside the territorial limits of the state where the explosion is conducted. The treaty enters into force on October 10, 1963.
1963 -- June 10: TEST BAN TALKS The United States, Britain, and the Soviet Union announce that high-level talks will be held in Moscow in July to seek agreement on a test ban. In a speech on the settlement of Cold War problems, President Kennedy says the United States will voluntarily suspend nuclear tests in the atmosphere pending negotiation of a test ban agreement, provided other countries follow suit.
1962 -- August 27: DRAFT TEST BAN TREATIES - The United States and Britain introduce two new draft test ban treaties. The first calls for a comprehensive ban on tests enforced by nationally manned control posts under international supervision and obligatory on-site inspection. The second, offered as an alternative, calls for a limited ban ending testing in all environments except underground and monitored by national technical means of verification without the need to establish any international verification machinery.
1962 -- March 2: U.S. ATMOSPHERIC TESTS - President Kennedy announces that the United States will resume atmospheric testing unless the Soviet Union agrees to the U.S.-British atmospheric test ban proposal by late April. In the absence of agreement, the United States resumes atmospheric testing on April 25.
1961 -- September 3: ATMOSPHERIC TEST BAN PROPOSAL - In response to Soviet resumption of nuclear tests in the atmosphere on September 1, President Kennedy and British Prime Minister Harold Macmillan urge the Soviet Union to agree to a ban on atmospheric tests. Premier Khrushchev rejects this proposal. The United States resumes underground nuclear testing less than two weeks later, on September 15.
1961 -- September 1: RESUMPTION OF SOVIET NUCLEAR TESTING - Arguing that increased international tensions and the French nuclear test program have created a changed security environment, the Soviet Union resumes atmospheric nuclear testing.
1961 -- April 18: CTB DRAFT TREATY - The United States and Britain introduce a draft CTB treaty at the Geneva negotiations proposing a ban on all nuclear tests except for underground explosions measuring less than 4.75 on the Richter scale. The plan further calls for a three-year moratorium on such underground tests while research on verification techniques continues. The Soviet Union rejects the verification provisions and presents counterproposals that are unacceptable to the United States and Britain.
1961 -- March 21: CONTINUATION OF CTB NEGOTIATIONS - After a policy review by the administration of U.S. President John F. Kennedy, the CTB negotiations between the United States, Britain, and the Soviet Union reconvene in Geneva. While the sides are close on many points, the United States and Britain call for 20 on-site inspections per year, while the Soviet Union proposes only three.
1960 -- February 13: FIRST FRENCH NUCLEAR TEST France explodes its first nuclear device at a test site in the Sahara Desert.
1960 -- May 2: U-2 INCIDENT A U.S. - U-2 reconnaissance plane is shot down over Sverdlovsk in the Soviet Union. Premier Khrushchev cancels a scheduled four-power Paris summit, and no further progress is made in the CTB negotiations for the balance of the Eisenhower administration.
1959 -- December 29: EXPIRATION OF U.S. MORATORIUM - President Eisenhower announces that when the U.S. nuclear testing moratorium expires at the end of 1959, we "consider ourselves free to resume nuclear testing," but that the United States will not resume testing without advance notice.
1959 -- August 28: SOVIET STATEMENT ON MORATORIUM - The Soviet Union states that it will not resume nuclear testing provided the Western powers continue to observe a moratorium.
1959 -- August 26 EXTENSION OF U.S. MORATORIUM President Eisenhower extends the voluntary one-year suspension of nuclear weapons testing by the United States to December 31, 1959.
1959 -- May 5: U.S. NUCLEAR TEST BAN In another letter to Premier Khrushchev, President Eisenhower urges technical discussions on the possibility of banning nuclear tests to a greater atmospheric height than that mentioned in his April 13 letter. The president again urges the Soviet Union either to accept the control measures that would make possible a complete ban on nuclear weapons tests or to agree to the U.S. proposal for a partial ban.
The president states that the United States is prepared to explore Premier Khrushchev's proposal for a predetermined number of inspections in the territory of the United States, Britain, and the Soviet Union, but adds that the number should be related to scientific facts and detection capabilities.
1959 -- April 13: U.S. NUCLEAR TEST BAN PROPOSAL - In a letter to Soviet Premier Nikita Khrushchev, President Eisenhower offers an alternative approach to a nuclear test ban: If the Soviet Union insists on a veto over an on-site control system to monitor underground detonations, the two sides could implement a test ban in phases, starting with a prohibition of nuclear weapons tests in the atmosphere up to 50 kilometers. Meanwhile, the negotiations could continue to resolve the political and technical problems associated with control of underground and outer space tests.
Premier Khrushchev rejects the proposal and suggests instead a CTB with a predetermined number of on-site inspections.
1958 -- October 31: CTB NEGOTIATIONS - The United States, Britain, and the Soviet Union begin negotiations on a comprehensive nuclear test ban at the Geneva Conference on the Discontinuance of Nuclear Weapons Tests. The United States and Britain begin a one-year testing moratorium, which the Soviet Union joins a few days later.
1958 -- August 22: SECOND U.S. NUCLEAR TESTING PROPOSAL - President Eisenhower announces that the United States is prepared "to negotiate an agreement with other nations which have tested nuclear weapons for the suspension of nuclear weapons tests and the establishment of an international control system." If this proposal is accepted in principle by the other nations that have tested nuclear weapons, "then in order to facilitate the detailed negotiations, the United States is prepared, unless testing is resumed by the Soviet Union, to withhold further testing on its part of atomic and hydrogen weapons for a period of one year from the beginning of the negotiations. "
1958 -- April 8-August 21: CONFERENCE OF EXPERTS - President Eisenhower proposes a Conference of Experts to examine the issues involved in verifying a nuclear test ban. The conference convenes on July 1 in Geneva with scientists from the United States, Britain, the Soviet Union, France, Canada, Czechoslovakia, Romania, and Poland. On August 21, the conference releases a report indicating that a comprehensive nuclear test ban (CTB) can be verified through a network of 160 monitoring stations and that nuclear tests in space out to 50 kilometers can be verified, but that current technology cannot detect tests in deep space.
1958 -- March 31: SOVIET TESTING MORATORIUM - The Soviet Union announces that it will unilaterally halt all nuclear tests provided Western nations also stop testing.
1957 -- August 21: U.S. NUCLEAR TESTING PROPOSAL U.S. President Dwight D. Eisenhower announces that the United States would be willing, as part of a first-step disarmament agreement, to suspend testing of nuclear weapons for up to two years under certain conditions and safeguards. These include Soviet acceptance of the U.S. call for a permanent cessation of the production of fissionable materials for weapons purposes and the installation of inspection systems to ensure compliance.
1954 -- April 2 INDIAN "STANDSTILL AGREEMENT" - Jawaharlal Nehru, prime minister of India, calls for a "standstill agreement" on nuclear testing, the first initiative of its kind.
August 29, 1949: The first Soviet nuclear test is conducted at a test site near Semipalatinsk in Kazakhstan
The first British nuclear test takes place October 3, 1952, near the Monte Bello Islands off Australia.
1945 -- July 16-October 3, 1952 FIRST NUCLEAR TESTS - The United States conducts the world's first nuclear weapons test, code-named Trinity, at Alamogordo, New Mexico.