Ten years ago, I deployed to a small Soviet-era training base in western Ukraine. My unit was there to train the Ukrainian Armed Forces on NATO doctrine and introduce them to American weapons systems and intelligence assets. Russian President Vladimir Putin’s full-scale invasion was still six years away, but the Ukrainians knew something was coming.

They were already rotating battalions east to fight in what they called the Anti-Terrorist Operation, defending their country against separatists whom Russia funded, trained, and, at times, fought beside.