Tensions between the US and European NATO allies

Questions about the US' commitment to its allies may have sparked a new nuclear age

Some US allies—from Warsaw to Seoul—are reevaluating their security amid doubts over American nuclear commitment, signaling the possibility they may want to acquire their own weapons.

NATO condemned Russia's 2022 invasion of Ukraine

While Ukraine is not a member, NATO responded forcefully to the Russian invasion of the country in 2022. This page from the NATO website offers answers to frequently asked questions about NATO’s response to the invasion, specifically on how NATO is aiding Ukraine.

Wartime conferences exposed cracks in the US–Soviet alliance

At the Tehran, Yalta and Potsdam Conferences, Allied leaders coordinated WWII strategy—but deep disagreements over postwar Europe foreshadowed the Cold War. The USSR’s push for influence in Eastern Europe clashed with US and British calls for self-determination.

Members decide to what extent they respond to an attack on an ally

The NATO constitution is intentionally vague about what exactly is required from its members. Explore the historical debates and learn more about common misconceptions about NATO’s common defense clause.

As of 2025, every NATO member spent at least 2% of GDP on defense, a target the alliance had been pushing toward for over a decade.

Finland and Sweden joined NATO after Russia's invasion of Ukraine

In response to Russia's 2022 invasion of Ukraine, Finland and Sweden abandoned decades of military neutrality to join NATO, marking a major shift in Europe's security landscape and expanding the alliance to Russia's borders.

Ukraine has received over $300B in Western military and financial aid

Although not a member of NATO, Ukraine has received substantial support from Western nations, primarily the United States and the European Union, totaling more than $300B in military, financial, and humanitarian assistance.

Germany is pursuing its most significant military buildup since WWII.

NATO was formed in 1949 to deter Soviet expansion, prevent European militarism, and encourage political integration.

NATO has only invoked its mutual defense clause once, in the days after the 9/11 attacks.

The treaty's Article 5 requires mutual defense, but not necessarily military action.

NATO consists of 32 countries across North America and Europe.

The global nuclear arms regime has slowly eroded over the past few decades

Both Russia and the United States have withdrawn from key Cold War-era arms-control pacts. Russia's 2022 invasion of Ukraine marked a turning point, as it suspended its participation in inspections and data-sharing agreements.

NATO leads cyber war games in Estonia

Estonia is host to one of the world’s largest annual interactive cybersecurity drills. Russia is always considered the main threat, but this year, the war in Ukraine has only added to the stakes.

Testing assumptions about the war in Ukraine, one year later

Two years ago, policymakers in Washington made multiple predictions about the course of the war between Russia and Ukraine. One year later this site revisited several common assumptions about the war—for example, that Russia would swiftly defeat Ukraine—and asks several experts if they came true, or not. But things can always change.

Putin claimed the invasion of Ukraine was to demilitarize and 'denazify' the country

In a 5,000-word historical treatise he wrote himself, President Vladimir Putin claimed the move was meant to restore Russia's historic lands. Many Western historians and global leaders described these narratives as false pretexts for aggression.

Modern Ukraine—caught between Europe and Russia

"Ukraine" has been translated by some scholars as meaning "borderlands". Indeed the country lies perfectly between Europe and Russia, while hosting a diverse collection of people of differing languages, cultures, and ethnicities, feeling affinity for those on the other sides of the country's borders. This article explores how this affects the actions and reactions of Ukrainians during the current conflict.

Breaking down Europe's reliance on Russian energy (preinvasion)

One side effect of the Russian-Ukraine conflict is how it underscored European dependence on Russian natural gas and oil. This article, published days before the Russian attacks, outlines and illustrated how much gas and oil flows from Russia to Europe and the potential for either side to use sanctions to get what they want.

The alliance operates under a "flexible response" doctrine—that is, proportionality

NATO countries' main deterrent against aggression is their ability to respond with nuclear weapons. This video from "The Infographics Show" outlines the purpose of this nuclear arsenal, NATO’s strategy to prevent attacks, and its plans in the event of escalation toward nuclear war.

Four Cold War hawks warn: Nuclear weapons still threaten the world

Despite the Cold War's end, the US and Russia still hold 95% of the world's nuclear weapons—many on hair-trigger alert. In this 2010 documentary, top former officials urge urgent action to reduce and eliminate the threat.

Decisions at NATO are by consensus and must be unanimous

There are two strategic commands in NATO: one in Europe (Supreme Allied Headquarters Command Europe) and another in Norfolk, Virginia (Allied Command Transformation). The alliance is headed by both a military officer and a civilian leader.

Many countries remained neutral after Russia's invasion of Ukraine

Following Russia's 2022 invasion of Ukraine, few nations outside the West imposed sanctions on Moscow. Major powers such as China, India, Brazil, and Turkey remained neutral, underscoring global divisions over how to confront Russian aggression.

Ukraine's pro-Russian President halted an EU deal in 2013, leading to a mass protest movement

In late 2013, President Viktor Yanukovych suspended preparations for a long-negotiated EU association agreement under Russian pressure, signaling a return to Moscow's influence and sparking mass Euromaidan protests across Ukraine.

Ukraine once had the third-largest nuclear arsenal—and gave them all up by 1996.

NATO's Article 5 has been invoked once—after 9/11

The article was invoked the day after the attacks and launched a series of NATO campaigns to fight global terrorism. This page includes excerpts from a speech by then-NATO Secretary General Jens Stoltenberg about the attacks and the organization’s response.

How NATO responded to 9/11

The collective defense clause of the NATO constitution has only been invoked one time: after the 9/11 terrorist attacks against the United States. This video explores the immediate actions NATO took to respond to the attacks to support the United States. These firsthand clips from 2001 give a sense of the magnitude of the moment and the difficult decisions facing NATO leaders at the time.

The origins of Putin's 'Nazism' claim in Ukraine

Ukraine has had a varied history, and is home to a rich diversity of ethnicities, religions, and people. In the time leading up to Russia's attacks on the country, Russian President Vladimir Putin referred to Ukraine as a "Nazi nation", owing to Ukrainian nationalists' acceptance of the invading Nazis as liberators from the Soviet Union in WWII. The history is more complex than that. Read this Smithsonian Magazine article to learn more.

Breaking down Western military weapons in Ukraine

Since the beginning of the Russian invasion of Ukraine in February 2022, Western military aid has helped dictate Ukraine's capability and strategy on the battlefield. From advanced ground-launched missiles to millions of rounds of ammunition, the supplies have been critical for Ukraine but force Western countries to tip-toe around the appearance of direct conflict with Russia. This visual deep-dive breaks down some of the most important military aid to date.

The Cold War (1947-1991) prompted the birth of NATO and the Soviet Warsaw Pact

The geopolitical rivalry between the United States and Soviet Union was considered “cold" because the two countries never directly engaged in military combat during the time period. This page from the Kennedy Presidential Library outlines the causes and major events of the early Cold War.

Much of the Global South responded to the Russia-Ukraine war by pursuing a strategy of 'active nonalignment'

Boston University scholar Jorge Heine suggests that countries across Africa, Asia, and Latin America are avoiding taking sides between Washington and Beijing—viewing the rules-based order as increasingly unresponsive to the needs of developing nations and considering the West's framing of the war irrelevant to its own interests.

Why is the Black Sea region strategically important?

This commentary is the first in a series of essays that examine the strategic significance of the Black Sea region to the US and NATO.

Explore over a century of US-Canadian relations.

Watch the historic treaty signing that established NATO in 1949

NATO was created with the signing of the North Atlantic Treaty on April 4, 1949, in Washington, DC. The clip embedded in the webpage includes a newsreel with an excerpt from US President Harry Truman’s speech celebrating the historic day.

The last remaining US-Russia nuclear arms treaty expired in February 2026

The New START treaty, which capped US and Russian strategic warheads at 1,550 each, expired on Feb. 5, 2026. Without formal limits, fears of a renewed arms race are rising, as both nations could deploy more weapons while follow-on talks continue.

Russia's invasion of Ukraine accelerated fractures in the rules-based international order

This piece examines how the Ukraine conflict intensified underlying divisions in the global order—between Western democracies and the Global South, and between rule-of-law norms and great-power politics.

During the Cold War and into the 21st century, US and Soviet/Russian leaders repeatedly agreed to arms control treaties, though strained tensions have led to the expiration of agreements in recent years.

A 1983 NATO war simulation provoked the Soviets to prepare for war

The "SNAFU" podcast, hosted by actor and comedian Ed Helms, explores some of the biggest blunders in history. Season one focuses on the 1983 NATO Able Archer military exercise, a war game that simulated nuclear attacks on the Soviet Union. The USSR mistook the exercise for a genuine threat and prepared its forces for war. Helms recounts this almost catastrophic event in world history with his signature humor.

US–Soviet hostility began long before the Cold War

US–Soviet tensions began decades before WWII. After the 1917 revolution, the US refused to recognize the Bolshevik regime and even sent troops to fight against it.

Proponents argue that abandoning the rules-based order risks a return to the chaos that led to 2 world wars

Brookings scholar Robert Kagan warns that if China and Russia gain regional dominance, the world could return to the unstable conditions of the late 19th century—the same chaos that led to two devastating world wars.

Language and regional differences are faults lines in Ukraine's conflict.

The 1955 Warsaw Pact was the Soviet Union’s answer to NATO

The pact included Albania, Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, Romania, and the USSR. The pact established collective security and a joint military command between the member countries.

The value of fracking is dependent on international energy markets

Russia's war in Ukraine spurred calls in the US to increase fracking, which has historically reduced dependence on foreign nations and increased national security. However, some experts argue that renewable energy provides even better energy independence, as fracking investments may not be worthwhile if importing fossil fuels is significantly cheaper.

The Russia-Ukraine conflict is the largest ground war in Europe since World War II in terms of casualties, forces mobilized, and displacement of civilians.

Nearly 90% of the world's 12,187 nuclear warheads are held by Russia and the United States.

President Trump invoked the Monroe Doctrine in 2025, announcing a new 'Trump Corollary'

On Dec. 2, 2025, the 202nd anniversary of the doctrine, President Donald Trump issued a proclamation reaffirming US "dominance" in the Western Hemisphere. His administration's national security strategy officially codified the "Trump Corollary," stating that the US would prevent non-hemispheric powers from gaining strategic influence in the Americas.

The Minsk peace accords failed to end fighting in eastern Ukraine in the mid-2010s

The Minsk Agreements of 2014 and 2015 sought to halt the war in eastern Ukraine through ceasefires and political reforms, but repeated violations left the accords unenforced and the conflict unresolved.

The day Russia invaded Ukraine—an oral history

Experience the slow build-up to the Russian-Ukraine war, to the moment when it was clear Putin intended to invade, to the actual invasion and occupation in this oral history compiled by Politico. Multiple US and Western officials share their perspectives and thoughts on the war, how it's been conducted, and what can happen next.

In 2024, the US committed about $82.3B to foreign aid.

That year, 67.2% of foreign aid was for economic purposes, and the remaining 32.8% was for military purposes. Israel received more US foreign aid than any other country in 2024.

Experts argue that nuclear war is more likely than is commonly believed

The podcast highlights that many of the world's roughly 12,000 nuclear weapons—capable of triggering global collapse and nuclear winter—remain on high alert. Experts warn that this status, combined with limited public awareness, makes nuclear war disturbingly plausible.

The US and South Korea have a robust, if delicate, alliance

The deep ties between South Korea and the United States go back decades, but the relationship hasn’t always been frictionless. When two off-duty American servicemen accidentally killed two South Korean middle-school girls in 2002, it set off anti-American protests that led South Korea to seek a more balanced relationship. The Council on Foreign Relations traces key moments in the two countries’ seven-decade history.