Six maps explaining the Ukraine-Russia conflict

Updated 11:35 AM ET, Fri February 25, 2022

(CNN)Russian President Vladimir Putin on Thursday began a military operation in Ukraine after weeks of warnings by Western powers that such an attack was imminent.

But Russia's invasion of Ukraine was also precipitated by years of rising tensions. Below are six maps that help illustrate the events that led to this moment.

NATO since the Cold War

Since the end of the Cold War, more countries have been joining the North Atlantic Treaty Organization, or NATO, pushing the bloc eastward.
In 2008, NATO declared its intention to offer membership to Ukraine -- a former cornerstone of the Soviet Union -- some day in the distant future. But Russia considered that crossing a red line.
This map shows NATO's expansion eastward in Europe. Many countries in western Europe joined prior to 1991 and the end of the Cold War, while those to the east -- including the former Soviet Baltic republics of Estonia, Latvia and Lithuania -- joined in the years since.
Putin has indicated he sees NATO's expansion as an existential threat, and the prospect of Ukraine joining the Western military alliance a "hostile act." He has emphasized his view that Ukraine is part of Russia, culturally, linguistically and politically, and Russia asked amid recent tensions for guarantees the European and North American defense alliance wouldn't expand further east.
The United States and NATO have resisted. The alliance's "open door policy" states that any European country ready and willing to undertake the commitments and obligations of membership is welcome to apply for membership. And since the end of the Cold War, more than a dozen countries from the former Eastern bloc have joined.

Annexing part of Ukraine

In early 2014, mass protests in the Ukrainian capital forced out a Russian-backed president after he refused to sign a historic political and trade agreement with the European Union.
Russia responded by annexing the Ukrainian peninsula of Crimea, highlighted in red along the Black Sea's northern coast in the map below, and fomenting