The START Agreements: Reducing Strategic Offensive Arms

In the early 1990s, the two largest nuclear powers on Earth held tens of thousands of warheads between them, enough to end civilisation many times over. Then something remarkable happened. Instead of building more, the United States and the Soviet Union signed agreements to start tearing weapons down. These were the START agreements, and they marked one of the most important turning points in the history of nuclear arms control. Understanding how they worked, what they achieved, and where they fell short tells us a great deal about how rival superpowers learned to manage the deadliest weapons ever invented.

From limiting arms to actually reducing them 🔗

To appreciate why START mattered, you need to know what came before it. During the 1970s, the superpowers negotiated the Strategic Arms Limitation Talks (SALT). As the name suggests, these agreements only limited the growth of nuclear arsenals. They put a ceiling on numbers but did not require either side to dismantle existing weapons.

START represented a fundamental shift in ambition. When negotiations began on June 29, 1982, U.S. President Ronald Reagan renamed the talks and proposed something far bolder: radical reductions, not merely limitations, in each superpower’s stockpiles of missiles and warheads. The very word “reduction” replacing “limitation” signalled a new era. The stated American goal was to achieve deep cuts in the most destabilising systems while securing a verifiable agreement that would enhance stability and reduce the risk of war.

The road there was long. The talks dragged on for nearly a decade, interrupted in 1983 when the Soviet Union walked away in protest over the deployment of intermediate-range missiles in Western Europe. Negotiations resumed in 1985, supported by a series of summits, and finally produced a comprehensive agreement.

START I: the first real cuts 🔗

The Strategic Arms Reduction Treaty, now known as START I, was signed in Moscow on July 31, 1991 by U.S. President George H. W. Bush and Soviet leader Mikhail Gorbachev. It was a bilateral treaty between the United States and the Soviet Union on the reduction and limitation of strategic offensive arms.

What made it historic was that it was the first treaty to actually require both sides to reduce their strategic nuclear weapons. Strategic weapons are the long-range systems designed to strike an enemy’s homeland: intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and heavy bombers.

The numbers behind the treaty 🔗

START I set hard ceilings on both warheads and the vehicles that deliver them. Each side was limited to 6,000 accountable warheads and 1,600 delivery vehicles, meaning missiles and bombers. To put that in perspective, both superpowers each had more than ten thousand deployed warheads in 1990, so this represented a substantial cut.

Importantly, START I did not eliminate entire categories of weapons. It set overall numerical limits and required deep cuts, but both countries were free to decide which specific systems to keep within those ceilings. This is a key distinction from the treaty that followed.

Verification: trust but verify 🔗

A treaty is only as good as your ability to confirm the other side is keeping its word. START I built in an elaborate verification system. It introduced mechanisms for mutual verification and inspection to ensure compliance. These included on-site inspections, data exchanges, and “national technical means” such as satellites.

The treaty came with a detailed Memorandum of Understanding that contained data on the numbers and locations of all strategic delivery vehicles, plus diagrams of associated facilities like bases and storage sites. The two sides also voluntarily agreed to stop encrypting and jamming missile test data so each could monitor the other. This transparency was revolutionary between two countries that had spent decades treating each other as mortal enemies.

The Soviet collapse and the Lisbon Protocol 🔗

Then history intervened. Just months after the treaty was signed, the Soviet Union dissolved in December 1991. This created an immediate problem: the Soviet nuclear arsenal was now scattered across four independent republics, namely Russia, Belarus, Kazakhstan, and Ukraine.

The solution was the Lisbon Protocol, which made these successor states parties to START I and arranged for all strategic nuclear warheads to be transferred to Russia or destroyed. Belarus, Kazakhstan, and Ukraine agreed to give up the weapons on their soil. This is one of the great non-proliferation successes of the era, turning three potential new nuclear states back into non-nuclear ones.

Because of these complications, START I only entered into force on December 5, 1994. The results were dramatic. By the time of full implementation in 2001, around 80 percent of all strategic nuclear weapons then in existence had been dismantled. The treaty remained in force until it expired on December 5, 2009.

START II: aiming even higher 🔗

Encouraged by this success, the two sides moved quickly to negotiate a follow-up. START II was signed by President George H. W. Bush and Russian President Boris Yeltsin on January 3, 1993. By this point the partner was Russia rather than the Soviet Union, reflecting the new political reality.

START II aimed to push reductions much deeper. It sought to lower each side’s deployed strategic warheads to a maximum of 3,500, down from the 6,000 ceiling under START I. Where START I capped arsenals, START II tried to cut them roughly in half again.

The de-MIRVing agreement 🔗

The most significant feature of START II was its attack on a particularly dangerous class of weapon. The treaty would have banned multiple independently targetable reentry vehicles (MIRVs) on intercontinental ballistic missiles. For this reason it is often called the “de-MIRVing agreement.”

Why target MIRVs specifically? A MIRVed missile can carry several warheads, each aimed at a different target. A single such missile can carry anywhere from a few to many warheads. Arms control experts consider land-based MIRVed missiles destabilising because they put a premium on striking first.

The logic is unsettling but straightforward. If one missile carrying many warheads can destroy several of the enemy’s missiles in their silos, then in a crisis each side faces a terrifying incentive to use those weapons before they can be wiped out, the so-called “use it or lose it” pressure. By banning MIRVs on ICBMs, START II was designed to remove this dangerous first-strike temptation and make the overall nuclear balance more stable. The treaty also required the elimination of all heavy ICBMs.

The treaty that never took effect 🔗

Here is the twist in the story. Despite being signed and even ratified by both countries, START II never entered into force. It holds the unusual distinction of being a fully signed and ratified treaty that was ultimately rendered dead.

The reasons came down to linked disputes. Russia had agreed to START II on the condition that the United States preserve the 1972 Anti-Ballistic Missile (ABM) Treaty, which limited missile defence systems. When the United States withdrew from the ABM Treaty, Russia announced on June 14, 2002 that it would no longer be bound by START II, just one day later. Almost a decade of effort to bring the treaty to life collapsed.

START II was effectively overtaken by the 2002 Strategic Offensive Reductions Treaty, also called the Moscow Treaty, which required both sides to reduce their deployed strategic arsenals to 1,700 to 2,200 warheads each by the end of 2012. However, that later treaty did not carry forward START II’s prohibition on MIRVs, so a key stabilising idea was lost along the way.

Why the START agreements mattered 🔗

Even with START II’s failure, the START process was a landmark in international relations. Together the treaties helped manage one of the most dangerous transitions of the twentieth century: the end of the Cold War and the decline of Soviet power.

A shift from confrontation to cooperation 🔗

The deeper significance lies in what the treaties represented. For most of the Cold War, arms control was episodic and constrained, shaped by rivalry rather than cooperation. There were long stretches with no binding, verifiable treaty governing strategic forces at all. START changed that. The deep, verified reductions it mandated showed that even bitter rivals could move toward a managed, cooperative approach to nuclear security.

The treaties locked reductions into place along with transparency and verification mechanisms, providing an indispensable instrument for managing the end of the Cold War. The verification regime created predictability where there had been suspicion. As one arms control expert observed, the lower the numbers of weapons fall, the more verification matters.

Progress without full disarmament 🔗

It is important to be realistic about what START achieved. Even after these deep cuts, both countries retained thousands of nuclear warheads, far more than enough to destroy each other. The START agreements did not abolish nuclear weapons, and they were never intended to. They reduced and managed arsenals rather than eliminating them.

This connects to a broader debate in international relations about disarmament. Under the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), the recognised nuclear states pledged to pursue general disarmament in good faith. The START treaties can be seen as partial fulfilment of that promise: meaningful steps in the right direction, even if the ultimate goal of a world without nuclear weapons remains distant. For a student of international relations, this captures a recurring theme: progress in global politics is often incremental, contingent on circumstances, and shaped as much by geopolitics as by good intentions.

A foundation for what came later 🔗

The START framework did not disappear. Its verification methods and counting rules became the template for future agreements. The New START treaty, signed in 2010, continued the process begun by START I and based its verification measures on the original 1991 treaty. In this sense, START I created the architecture that successive treaties built upon, demonstrating how a single well-designed agreement can shape arms control for decades.

Putting it all together 🔗

The START agreements tell a story of both achievement and limitation. START I succeeded brilliantly, becoming the first treaty to actually reduce strategic arsenals, dismantling around 80 percent of the world’s strategic warheads, and managing the dangerous scattering of Soviet weapons after 1991. START II reached for more, attempting to ban the destabilising MIRVed missiles, but fell victim to the politics of missile defence and never came into effect.

Taken together, they represent a decisive move away from an unchecked arms race toward a more cooperative and managed approach to nuclear security between the superpowers. They reduced the risk of nuclear war, built habits of transparency and verification, and demonstrated a genuine commitment to the principle of disarmament, even while substantial arsenals remained. For anyone studying nuclear proliferation and international relations, the START agreements remain a key case study in how states cooperate even amid deep mistrust.

What do you think? If a treaty as carefully negotiated as START II could collapse over a linked dispute about missile defence, what does this tell us about the fragility of arms control agreements? And do verified reductions that still leave thousands of warheads in place count as meaningful progress toward disarmament, or merely as better management of the threat?

References

1. https://en.wikipedia.org/wiki/Strategic_Arms_Limitation_Talks
2. https://www.britannica.com/event/Strategic-Arms-Reduction-Talks
3. https://www.acq.osd.mil/asda/ssipm/sdc/tc/start1/start1-aaa/START1lett-sub.html
4. https://2001-2009.state.gov/r/pa/ho/time/pcw/104210.htm
5. https://www.armscontrol.org/treaties/strategic-arms-reduction-treaty-i
6. https://goodauthority.org/news/good-to-know-as-new-start-expires-whats-next/
7. https://www.ebsco.com/research-starters/diplomacy-and-international-relations/start-treaty-signed
8. https://www.armscontrol.org/factsheets/start-i-glance
9. https://armscontrolcenter.org/strategic-arms-reduction-treaty-start-i/
10. https://en.wikipedia.org/wiki/START_I
11. https://nps.gov/articles/start-treaty-1991.htm
12. https://armscontrolcenter.org/strategic-arms-reduction-treaty-ii/
13. https://www.history.com/articles/start-nuclear-treaties
14. https://en.wikipedia.org/wiki/START_II
15. https://military-history.fandom.com/wiki/START_II
16. https://www.nti.org/education-center/treaties-and-regimes/treaties-between-united-states-america-and-union-soviet-socialist-republics-strategic-offensive-reductions-start-i-start-ii/
17. https://www.armscontrol.org/factsheets/start-ii-and-its-extension-protocol-glance
18. https://www.justsecurity.org/131851/arms-control-after-new-start/
19. https://www.fpri.org/article/2009/05/arms-control-in-the-cold-war/
20. https://www.cfr.org/timelines/us-russia-nuclear-arms-control
21. https://www.armscontrol.org/factsheets/new-start-glance