It’s been a year since Russia invaded Ukraine, and the battle continues. Military and civilian deaths and injuries on both sides have been estimated in the hundreds of thousands, and millions more Ukrainians have been displaced. What set the stage for today’s conflict? Here’s a look back at the long, intertwined history of the contentious neighbors.

The two countries’ shared heritage goes back more than a thousand years to a time when Kyiv, now Ukraine’s capital, was at the center of the first Slavic state, Kyivan Rus, the birthplace of both Ukraine and Russia. In A.D. 988 Volodymyr the Great, the pagan prince of Novgorod and grand prince of Kyiv, accepted the Orthodox Christian faith and was baptized in the Crimean