Behind the scenes and on-camera, combustible personalities and shifting politics in the U.S. and Europe resulted in decisions on security that could echo for years - including reopening the debate on nuclear weapons.

European leaders have been working to support Ukraine and beef up their own defenses. But the blowup between President Trump and Ukraine’s president on Friday made those goals more urgent.

President Trump this week suspended U.S. military assistance and intelligence sharing with Ukraine, just days after a contentious Oval Office meeting in which he publicly berated Ukrainian President Volodymyr Zelensky for failing to cooperate with his plan for a cease-fire with Russia.