Warning: this episode contains descriptions of war. When Ukrainian troops crossed over into Russia two weeks ago, it appeared at first to be a largely symbolic gesture. But in the time since, it has emerged as a potentially pivotal moment in the war. Andrew Kramer, the Kyiv bureau chief for The Times, explains what’s behind the audacious Ukrainian operation, and Anton Troianovski, the Moscow bureau chief, explains how Russia’s response could reshape the conflict. Guest: Andrew E. Kramer, the Kyiv bureau chief for The New York Times. Anton Troianovski, the Moscow bureau chief for The New York Times.