The invasion of Ukraine by Russian forces has spurred Europe’s worst security crisis in decades. But while most analysis is rightly focused on the immediate situation, it is equally important to forecast the war’s multiple possible trajectories and outcomes. Anticipating the uncertainties that this war will bring is a critical …

NATO airspace will not be used to transfer fighter planes to the Ukrainian military, alliance leaders said Tuesday after a meeting in Poland, where top U.S. commanders were on hand for high-level security talks. Ukraine has requested additional military hardware from the West to help stave off Russia’s full-scale invasion, …

Roughly 80% of the more than 170,000 troops Russia had surrounding Ukraine for months before invading are now inside the country, though the Ukrainian resistance and supply issues have slowed their advance, a senior U.S. defense official said Tuesday. Russian forces advancing toward Ukraine’s capital of Kyiv “has made no …