BRUSSELS (AP) — Since Russian President Vladimir Putin ordered the invasion of Ukraine in 2022, NATO has focused on trying to deter an attack on its own territory and avoid all-out war with nuclear armed Russia. Now the time has come for NATO to defend itself, and European allies might have to do it alone, experts and leaders say.

"If any troops appear there, especially now while fighting is ongoing, we assume that they will be legitimate targets," Putin says as the U.S. and Europe plan for a post-war Ukraine.