The phone connection from my living room to the eastern Ukraine battlefield couldn¡¯t have been better. First Lieutenant Alexei Chaban of the Ukrainian 17th Tank Brigade came in clear amid sounds of gunfire in the distance.

¡°There¡¯s some shelling going on,¡± he said. ¡°If the line cuts out, it¡¯s a mortar attack.¡± Chaban spoke in the same matter-of-fact voice of his Facebook posts from the front. Chaban, 50, has become an Internet sensation since he posted an open letter to the mother of a Russian tank commander whose life he had spared during a skirmish last week.

When I told him last week that his letter had already been ¡°shared¡± 17,000 times and ¡°liked¡± by 8,000 Facebook users, Chaban was taken aback. His mobile Internet connection is excruciatingly slow, he said, so he had had no idea how popular he had become.