The leaders of the 27 European Union countries will hold an emergency summit on March 6 about next steps for Ukraine and Europe’s security.

In the shadow of imminent defeat, European powers have unveiled their most audacious military initiative since the end of World War II. As Russia tightens its grip on Ukraine, Britain and France are preparing to cross a line that could potentially reshape the continent's security landscape forever.

Political and military leaders in Europe are fleshing out details of a plan for European forces to help ensure Moscow does not attack Ukraine again once the guns fall silent.