European leaders met in London to form a plan to help end the war in Ukraine. But even potential peacekeepers face political and economic hurdles.

Even as they have rallied to Volodymyr Zelenskiy's side after his Oval Office clash with Donald Trump, European leaders' approach to the war in Ukraine and the continent's security remains highly dependent on the U.

In a war dominated by the unexpected, few imagined Ukraine’s fourth year at war would so firmly now question the security of all of Europe.