Vladimir Putin puts Russian nuclear forces on alert amidst Ukraine invasion RELATED: The sights, sounds and stories from Ukraine https://youtu.be/4ki_uLUM8qU President Putin ordered Russian nuclear forces to be on high alert as Kharkiv, Ukraine's second-largest city, is assaulted by Russian troops. » Subscribe to USA TODAY: http://bit.ly/1xa3XAh » Watch more on this and other topics from USA TODAY: https://bit.ly/3HkPSus » USA TODAY delivers current local and national news, sports, entertainment, finance, technology, and more through award-winning journalism, photos, videos and VR.