In August 2014, after months of increasingly assertive intervention into the Ukraine crisis, Russian President Vladimir Putin crossed a major line by invading the country's rebel-held east with Russian tanks and troops. Vox Foreign Editor Max Fisher explains Putin's reasons for invading are less obvious than you might think.

Produced by Joe Posner & Joss Fong
Photographs courtesy Getty Images

Subscribe to our channel! http://www.youtube.com/subscription_center?add_user=voxdotcom

Vox.com is news website that helps you cut through the noise and understand what's really driving the events in the headlines. Check out http://www.vox.com to get up to speed on everything from Kurdistan to the Kim Kardashian app.

Follow Vox on Twitter: https://twitter.com/voxdotcom
Or on Facebook: https://www.facebook.com/Vox