Russia annexed the Crimea in 2014 after troops without insignia occupied crucial infrastructure, including Ukrainian military bases, while Ukrainian troops put up little resistance and retreated. It was only years later that Russian President Vladimir Putin publicly admitted that these were in fact Russian troops.
Activists in eastern Ukraine, backed by Russian operatives, took over towns and tore down Ukrainian flags. Separatist leaders in the cities of Donetsk and Luhansk held elections supporting a motion to break away from Ukraine.
Sporadic violence grew into a full-blown conflict in May 2014, when Ukraine launched an airstrike on the Donetsk airport that was overrun by Russian Chechen fighters. More than 10,000 people have been killed and over 1 million displaced, with large parts of the east still under separatist control. The Kremlin never admitted its role, portraying it as a civil conflict, but overwhelming evidence suggests Russia has been sending a sizeable number of troops and advisers as well as weapons to the rebels.
Ukraine signed peace accords with the separatists in 2015, calling for a cease-fire and political settlement in the east. While it helped to decrease the intensity of fighting, the accords did nothing to resolve the region's political stalemate.