Russian forces invaded Ukraine early on February 24, 2022, following an ominous yearlong military buildup and 30 years of Ukrainian independence after the Soviet Union fell apart in December 1991. The country of nearly 45 million people, assaulted from Belarus to the north, Russia to the east, and Russian-controlled Crimea in the south, is strategically positioned between Russia and the rest of Europe—including a swath of eastern European nations once under the Soviet sphere that have since joined the North Atlantic Treaty Organization, an expansion of the Western defensive alliance that Russia views as a profound threat.

Russian interventions in other former Soviet-bloc countries have led to several still disputed regions known as “frozen conflict” zones, including along Ukraine’s border. Ukraine