How Has NATO’s Post–Cold War Expansion Contributed to Tensions with Russia?

To understand why Russia sees NATO as a threat—and why Ukraine’s relationship with NATO played a key role in triggering war—you need to look back at what happened after the Cold War ended. When the Soviet Union collapsed in 1991, the world map changed, but so did the security landscape of Europe. And not everyone agreed on what that future should look like.

As Ukraine leaned westward toward NATO, Russia viewed the shifting map of alliances as a direct threat.

NATO Was Originally Formed to Contain the USSR

Let’s rewind to the beginning. NATO—the North Atlantic Treaty Organization—was created in 1949 to stop the spread of Soviet influence in Europe. It was a military alliance built on collective defense: if one member was attacked, all would respond.

During the Cold War, NATO stood on one side, and the USSR and its allies in the Warsaw Pact stood on the other. It was a standoff, and everyone knew where the lines were drawn.

The Cold War Ends—Now What?

When the Soviet Union collapsed, so did the Warsaw Pact. Suddenly, Eastern European countries that had once been under Soviet control were free to choose their own paths—and many of them turned westward, toward NATO.

Starting in 1999, former Eastern Bloc countries began joining the alliance. Poland, Hungary, and the Czech Republic went first. Then came others: Estonia, Latvia, Lithuania, Romania, Bulgaria, and more. Eventually, NATO had expanded right up to Russia’s borders.

Russia’s Perspective: A Broken Promise?

Russia saw this expansion as a betrayal. Many Russian officials claim that Western leaders had informally promised not to expand NATO eastward during talks in the early 1990s. Whether such a promise was ever made in writing is still debated, but the perception in Moscow was clear: NATO was encroaching.

To Russian leaders—especially Vladimir Putin—NATO’s growth looked less like peaceful integration and more like encirclement. He began calling it a threat to Russia’s national security.

Ukraine’s Position: Stuck in the Middle

Ukraine, geographically and politically, has been caught in the middle. After gaining independence in 1991, it maintained a neutral stance for a while. But as time went on, especially after the Orange Revolution (2004) and Euromaidan (2013–14), Ukraine’s leadership and people showed increasing interest in moving closer to the West.

This included closer ties with NATO—though Ukraine never officially became a member. It did, however, start participating in NATO training, joint operations, and signed cooperation agreements.

“NATO didn’t move toward Russia—Russia stood still while the rest of Europe moved on. And Ukraine refused to be left behind.”

That was too much for Russia.

In Putin’s eyes, Ukraine joining NATO would mean hostile military forces right on Russia’s doorstep. He often cites this as one of the key reasons for invading Crimea in 2014 and launching the full-scale invasion in 2022.

But Ukraine Has the Right to Choose

Here’s the part that gets overlooked: Ukraine is a sovereign nation, and like any other country, it has the right to decide its own alliances and future. Many Ukrainians see NATO not as a threat, but as protection—especially after what happened with Crimea and the war in the Donbas.

To them, joining NATO is a way to stay safe from Russian aggression—not provoke it.

A Security Dilemma

What we’re seeing here is a classic security dilemma. One side tries to increase its security (Ukraine seeking NATO protection), but the other side feels threatened (Russia), and that leads to conflict. It’s a vicious cycle.

But the historical context is key: NATO didn’t expand by force. Countries applied to join voluntarily, often because they feared what Russia might do if they didn’t.

Final Thoughts

NATO’s post–Cold War expansion didn’t create the conflict between Russia and Ukraine—but it became one of the major flashpoints. It highlighted deeper issues: Russia’s unwillingness to let go of its old empire, Ukraine’s desire to chart its own course, and the fragile balance of security in post-Soviet Europe.

The irony? NATO expansion was supposed to make Europe safer. Instead, it exposed just how unfinished the Cold War really was.