The incursion was the first time alliance planes had engaged enemy targets in NATO airspace. Poland’s leader called it “a large-scale provocation.”

Talks of a cease-fire in Ukraine have centered on the Donbas, a valued region for both sides and where most of the fighting is taking place. Michael Schwirtz, a global intelligence correspondent, and Anatoly Kurmanaev, a foreign correspondent covering Russia, break down who the Donbas is important to and why.