Geopolitical · 1945 — Present

Russia & the United States

86%

Share of the world's nuclear warheads held by the U.S. and Russia combined (FAS, beginning of 2026). New START, the last treaty capping them, expired in February 2026.

The rivalry that defined the 20th century never really ended — it just went quiet, then came back. For four decades the U.S. and the Soviet Union divided the world; the Cold War's end in 1991 promised a partnership that curdled instead into renewed confrontation, now centered on Ukraine and a still-vast nuclear balance. This traces the arc from the Cold War through the post-1991 thaw to today's refreeze — the arms race and its treaties, the proxy conflicts, the economic and cyber fronts, and why the two arsenals still hold the world's fate. Deep spine, live stakes.

Share of world nuclear warheads

86%

U.S. + Russia combined, total-inventory basis (FAS, beginning of 2026)

The Cold War

years — Truman Doctrine (1947) to Soviet dissolution (1991)

U.S. security aid to Ukraine

$67.8B

committed February 2022 — March 2026 (SIG-OAR via CRS)

U.S. vs Russian military spending

5.0×

$954B vs $190B in 2025 (SIPRI)

Bilateral goods trade

$4.4B

2025 two-way — down 88% from 2021 (Census)

The rivalry · 1945 — present

Hover any milestone for context.

OriginsCrisis / refreezeTreatyThaw

The shaded band marks the Cold War proper — the Truman Doctrine in March 1947 to the Soviet dissolution in December 1991.

How the world got divided

The alliance that beat Germany did not survive the peace. At Yalta in February 1945 and Potsdam that July, Roosevelt, Churchill, and Stalin settled the shape of postwar Europe — and in doing so drew the line that would hold for the next four decades. Within two years the wartime partnership had inverted into a standoff. In March 1947 Truman asked Congress to fund Greece and Turkey against communist pressure, and containment became American grand strategy. Most historians date the Cold War from that speech.

What made it different from every previous great-power rivalry arrived in the same summer as Yalta. The U.S. tested the first nuclear weapon in July 1945 and used two on Japan in August, opening a monopoly that lasted four years. When the USSR tested RDS-1 in August 1949 — years earlier than U.S. intelligence had forecast — the rivalry acquired the feature that still defines it: both sides could destroy the other, and neither could defend against it.

The arms race, in one number

The chart below is the whole Cold War in a single shape. The U.S. stockpile peaked at 31,255 warheads in 1967. The Soviet stockpile kept climbing for another two decades and peaked at 40,159 in 1986 — a year after Gorbachev took power, and a year before the INF Treaty eliminated an entire class of missiles. At the 1986 high-water mark the two held 63,476 warheads between them.

The lines cross five times, which is the detail most summaries lose. The Soviets pulled ahead in 1978 and stayed ahead through the end of the USSR. Treaty-driven cuts put the U.S. back in front in 2002; Russia retook the lead in 2007, lost it again in 2011, and has held it since 2016. The lead has changed hands repeatedly, and it has never meant much — Russia's numerical edge today has more to do with tactical weapons and dismantlement pace than with strategy.

The proxy wars

The two never fought each other directly. That is the single most important fact about the Cold War, and it is why the era's violence shows up somewhere other than in a U.S.—Soviet casualty count. Korea (1950—53), Vietnam (1955—75), Afghanistan (1979—89), and a long list of interventions across Latin America, Africa, and the Middle East were where the rivalry was actually fought — each one a local conflict that both superpowers armed, funded, and used to test the other's resolve.

The pattern is symmetrical enough to be uncomfortable. The U.S. armed the mujahideen against the Soviets in Afghanistan; the Soviets armed the North Vietnamese against the U.S. Each superpower's proxy war became the other's demonstration that the rivalry had costs. The Soviet withdrawal from Afghanistan in 1989 preceded the collapse by two years — a sequence Moscow has not forgotten, and one that features in Russian arguments about Western intentions to this day.

Nuclear stockpile · 1945 — 20261991 = USSR dissolves

USSR / RussiaUnited States

Source: FAS, Estimated Global Nuclear Warhead Inventories — charted from 1945, the first year of the series. Military-stockpile basis (deployed + reserve); FAS's larger "total inventory" adds retired warheads awaiting dismantlement. The USSR enters in 1949 with a single warhead.