The US pledged to 'defend every inch of NATO territory' after Russia's invasion of Ukraine. So which countries does that include?

• The US and NATO pledged to protect "every inch of NATO territory" amid Russia's assault on Ukraine.
• Ukraine has expressed interest in joining the alliance but has never been formally admitted.

When Russia invaded Ukraine a year ago last February, the National Atlantic Treaty Organization swiftly condemned the unprovoked assault as a war of aggression against Ukraine, a sovereign and peaceful country.

While Ukraine is not a NATO member, it is a NATO partner country, and the treaty has helped to coordinate aid and assistance to Ukraine over the last 12 months, while continuing to assure the protection of individual member countries, many of which have sent weapons, money, and military equipment to help Ukraine fight.

Following Putin's February 24, 2022 invasion, President Joe Biden said no US troops would be sent to Ukraine, though he warned that the US and its allies would "defend every inch of NATO territory." The president also announced that some US troops would be sent to the Baltics to bolster NATO positions in the east.

"Our forces are not and will not be engaged in the conflict with Russia in Ukraine," Biden said in a February 2022 speech from the White House. "Our forces are not going to Europe to fight in Ukraine, but to defend our NATO allies."

As scores of Ukrainians fled to neighboring countries in the weeks and months following the invasion, the conflict rapidly expanded into the most serious armed conflict in Europe in decades.

What is NATO?

The North Atlantic Treaty Organization is a military alliance created in 1949 to provide collective security against Soviet expansionism and to encourage European political integration in the aftermath of World War II.

NATO serves as a collective security system, wherein its member states agree to mutually defend any attack on a member party by any external actor.

The agreement contained just 12 countries when it was founded but has more than doubled in size in the years since. The alliance now consists of 28 European countries and two countries in North America.

Following the invasion, the organization condemned what it called Russia's "horrifying attack on Ukraine," accusing President Vladimir Putin of violating international law in an act of aggression against an independent peaceful country. A statement from NATO said the organization had agreed to "take additional steps" to strengthen deterrence and protect all allies, but details on its next steps have been notably vague.

"We stand united to defend each other," the organization said in the statement.

In the year since the war began, Putin has several times warned Western nations not to involve themselves in the war, even issuing veiled nuclear threats late last year, with experts telling Insider the Russian president was likely trying to manipulate global fear and scare the West into ramping down or discontinuing its aid to Ukraine.

Ukraine isn't a member of NATO, but it wants to be

Ukraine has expressed a desire to join NATO but has yet to be formally admitted.

The body has designated the former Soviet country as one of its "enhanced opportunity partners," a title granted to nonmember countries that have contributed to NATO-led operations and missions.

But ongoing unrest in the country, even before 2022, worried some NATO members — such as France and Germany, both of which have previously opposed Ukraine's inclusion — and a new NATO member can be inducted only by unanimous consent.

Russian leaders — Putin in particular — have long been wary of NATO's eastward expansion, especially after the alliance granted membership to former Soviet nations in the late 1990s and early 2000s. Tensions escalated even further in 2008 when NATO announced its intent to admit both Ukraine and Georgia at an undetermined future time.

Ukraine's former Soviet status and close historical ties to Russia made NATO membership for the country a firm line in the sand for Putin, who said in 2008 that its inclusion in the alliance would be viewed as a "hostile act toward Russia."

As such, NATO and its members have no legal obligation to act on Ukraine's behalf.

But Ukrainian President Volodymyr Zelensky has appealed directly to NATO members in the year since Russia's invasion — a plea, he said, that was initially met with silence.

"Today I asked the 27 leaders of Europe whether Ukraine will be in NATO, I asked directly," he said during a February 2022 speech. "Everyone is afraid, does not answer. And we are not afraid, we are not afraid of anything."

Allowing Ukraine to join NATO at the current moment would require all NATO members to come to Ukraine's immediate defense, prompting near-global war against Russia.

Belarus — Ukraine's northern neighbor and a close Russian ally — isn't a member of NATO

Belarusian President Aleksandr Lukashenko, a longtime ally of Putin, allowed Russian forces to invade Ukraine via Belarus.

While Lukashenko said Belarusian troops didn't join the conflict, Russian forces used Belarusian territory to enter Ukraine from the north, with Belarusian border guards and the country's air-defense system available to Moscow.

Lukashenko said last year that his country's forces would join the action "if it is necessary for Belarus and Russia," and he reiterated his claims earlier this month. The state-owned Russian news agency TASS reported in February 2022 that Lukashenko received assurances from Putin that any attack against Belarus would constitute an attack on Russia as well.

Belarus is a member of the Collective Security Treaty Organization — Russia's counter to NATO — which is its own intergovernmental military alliance in Eurasia that includes certain post-Soviet countries.

Moldova has no plans to formally join NATO

In the immediate aftermath of last year's invasion, thousands of Ukrainian refugees flocked to Moldova, located to the southwest of Ukraine.

The country's president said the government deployed temporary placement centers for incoming migrants and stressed that Moldova's borders were open for Ukrainian citizens "who need safe transit or stay."

But despite the small nation's support for fleeing refugees, unlike Ukraine, the former Soviet country has no plans to formally join NATO.

Written into Moldova's constitution is an enshrinement of neutrality: "The Republic of Moldova proclaims its permanent neutrality. The Republic of Moldova does not allow the deployment of armed forces of other states on its territory."

The country does, however, cooperate with NATO on a range of issues, according to the alliance's website, primarily in its efforts to reform and modernize its defense and security structures.

Poland has been part of NATO since 1999

Ukraine's northwestern neighbor quickly a key player in the conflict, as thousands of Ukrainian refugees seek solace in the NATO-protected European Union member.

The country was also the primary destination for more than 5,000 US troops that arrives in Eastern Europe leading up to the invasion. Following the start of the war, Poland's defense ministry introduced a high alert level, requiring service members in operational and territorial defense forces to stay in their units, The New York Times reported.

Poland, which was already home to more than 1 million Ukrainians prior to the war, has since welcomed approximately 1.5 million of the more than 8 million Ukrainian refugeeswho fled the country in the weeks and months following the invasion.

An analysis published in Foreign Policy speculated in February 2022 that Poland's capital, Warsaw, was set to become "the linchpin of the West's efforts to project power in Eastern Europe."

Should Putin succeed in taking control of Ukraine, a new battle line in Central Europe would be drawn. Russian forces could be stationed along Poland's eastern border, posing significant geopolitical ramifications and considerations for NATO countries, which have pledged to take action if one of their own is attacked.

Ukraine's 3 other western neighbors are members of NATO

Slovakia, Hungary, and Romania share a border with Ukraine and are all members of NATO. Hungary joined the organization in 1999, while Slovakia and Romania were granted membership in 2004.

All three countries have also accepted incoming Ukrainian refugees.

Putin's desire to keep NATO far from Russia has significantly backfired in the year since war broke out. Finland and Sweden, two longtime proponents of neutrality, changed their tune in the face of war, expressing a wish to join the body.

NATO formally invited both countries to join the alliance in June 2022.

Here is a full list of NATO members and the year they joined the organization:

• Albania: 2009
• Belgium: 1949
• Bulgaria: 2004
• Canada: 1949
• Croatia: 2009
• Czech Republic: 1999
• Denmark: 1949
• Estonia: 2004
• France: 1949
• Germany: 1955
• Greece: 1952
• Hungary: 1999
• Iceland: 1949
• Italy: 1949
• Latvia: 2004
• Lithuania: 2004
• Luxembourg: 1949
• Montenegro: 2017
• Netherlands: 1949
• North Macedonia: 2020
• Norway: 1949
• Poland: 1999
• Portugal: 1949
• Romania: 2004
• Slovakia: 2004
• Slovenia: 2004
• Spain: 1982
• Turkey: 1952
• United Kingdom: 1949
• United States: 1949