Concern over NATO's eastward expansion

The purported motivation for Russia's military invasion of Ukraine was the eastward expansion of the North Atlantic Treaty Organisation (NATO). Putin has expressed alarm over NATO's (North Atlantic Treaty Organization) expansion into Eastern Europe and former Soviet republics, particularly Ukraine.

NATO is a political and military alliance founded in 1949, with 30 member countries including the United States, Canada, the United Kingdom, France, Belgium, and many other European states. NATO membership is accessible to any European country that meets the organization's requirements. According to the alliance, Ukraine is one of three states considered aspiring members. Putin has criticized NATO's eastward expansion since the Soviet Union's collapse in 1991. He has stated that NATO joining states near Russia's borders is a provocation, despite NATO's assurance that it is a defensive alliance and not a danger to Russia.

One report stated: “Putin claimed that the eastward expansion of the Western alliance was a major factor in his decision to send troops to Ukraine’s border". Putin also stated in one speech that the invasion of Ukraine was in self-defense against NATO expansion.