A part of the NATO treaty could turn Russia's invasion of Ukraine into a wider war

Lloyd Austin, Dmytro Kuleba
Ukraine's Foreign Minister Dmytro Kuleba meets with Defense Secretary Lloyd Austin at the Pentagon, Tuesday, Feb. 22, 2022, in Washington. (AP Photo/Manuel Balce Ceneta)

As Russia began its invasion of Ukraine, some U.S. officials and analysts were already warning of a possible escalation of the conflict into a wider war.

The trigger: Article 5 of the North Atlantic Treaty.

As the fighting continues, we unpack what Article 5 is, what could invoke it, and the places and people to watch.