START I Treaty (1991): Cutting Strategic Nuclear Arsenals

The START I Treaty, signed in Moscow on 31 July 1991, was the first agreement in which the United States and the Soviet Union committed to reducing their strategic nuclear arsenals, not just limiting their growth. Presidents George H. W. Bush and Mikhail Gorbachev agreed to cut each side’s long-range forces to 1,600 delivery vehicles and 6,000 accountable warheads. Backed by an unprecedented system of inspections, it shaped nuclear arms control for nearly two decades.

Background: from limits to reductions

Earlier agreements, notably SALT I in 1972 and the unratified SALT II of 1979, had capped the number of missile launchers but allowed arsenals to keep growing. By the late 1980s each superpower deployed roughly 10,000 to 12,000 strategic warheads, depending on how they are counted.

President Ronald Reagan proposed Strategic Arms Reduction Talks (START) in May 1982, and negotiations opened in Geneva at the end of June that year. The Soviet delegation walked out in November 1983 in protest at the deployment of American intermediate-range missiles in Western Europe. Talks resumed in March 1985, shortly after Gorbachev became Soviet leader.

At the Reykjavik summit in October 1986, Reagan and Gorbachev came close to agreeing sweeping cuts but deadlocked over missile defence. The INF Treaty of 1987, which eliminated a whole class of intermediate-range missiles, showed that deep reductions and intrusive verification were achievable. START took four more years of negotiation, led in its final phase by Richard Burt for the United States and Yuri Nazarkin for the Soviet Union.

Terms of the treaty

The treaty set ceilings to be reached within seven years of its entry into force:

The 1,540 limit on heavy missiles meant halving the Soviet force of large SS-18 intercontinental missiles, a long-standing American demand. Washington regarded these ten-warhead missiles as the Soviet weapons best suited to a disarming first strike against American missile silos, so reducing them was central to its idea of a more stable balance. The throw-weight cap, a measure of how much payload missiles could lift, was set at roughly half the existing Soviet level.

Counting rules softened the numbers. A heavy bomber carrying gravity bombs or short-range missiles was counted as a single warhead however many weapons it carried, so the real number of deployed weapons could exceed 6,000. Even so, the treaty required each side to cut its strategic warheads by roughly a third or more.

Verification

START I’s verification regime was its most important innovation. It provided for regular data exchanges, notifications of missile movements, a dozen types of on-site inspections, and continuous monitoring of missile production facilities at Votkinsk in Russia and Magna, Utah. Each side also agreed to share telemetry, the data transmitted by missiles during test flights, and not to encrypt it.

The Soviet collapse and the Lisbon Protocol

Within weeks of the signing, the August Coup shook the Soviet state, and by the end of 1991 the USSR had dissolved. Strategic nuclear weapons were now located in four independent countries: Russia, Ukraine, Belarus and Kazakhstan.

The Lisbon Protocol, signed on 23 May 1992, made all four parties to the treaty. Ukraine, Belarus and Kazakhstan undertook to join the Nuclear Non-Proliferation Treaty as non-nuclear-weapon states and to transfer or eliminate the weapons on their territory. After long negotiations, particularly with Ukraine, START I entered into force on 5 December 1994. All three countries were free of nuclear weapons by the end of 1996.

Implementation and legacy

Both the United States and Russia reported that they had met the treaty’s limits by the deadline of 5 December 2001. The inspections continued until the treaty expired on 5 December 2009.

Its successor START II, signed in January 1993, would have banned multiple-warhead land-based missiles but never entered into force. The 2002 Moscow Treaty set lower limits without its own verification rules. New START, signed in Prague on 8 April 2010, borrowed heavily from START I’s inspection system.

Timeline

• 1982, May: Ronald Reagan proposes Strategic Arms Reduction Talks.
• 1983, November: Soviet negotiators walk out of the Geneva talks.
• 1985, March: Negotiations resume under the Nuclear and Space Talks.
• 1986, October: The Reykjavik summit ends without agreement.
• 1991, 31 July: Bush and Gorbachev sign START I in the Kremlin.
• 1992, 23 May: The Lisbon Protocol brings in Russia, Ukraine, Belarus and Kazakhstan.
• 1994, 5 December: START I enters into force.
• 2001, 5 December: Deadline for the reductions, met by both sides.
• 2009, 5 December: The treaty expires.

Why it matters

START I turned arms control from managing growth into cutting arsenals, and its inspections built a degree of transparency between former adversaries. Through the Lisbon Protocol it also helped ensure that the Soviet collapse produced one nuclear successor state rather than four.