Ukrainian soldiers at an anti-aircraft defense unit in the Donetsk region of Ukraine, Dec. 22, 2025. With talks on ending the Ukraine war making little progress on the toughest issues, Russia issued a dramatic threat on Monday, Dec. 29, to harden its stance, linking the potential change to what the Kremlin called a failed Ukrainian drone attack overnight targeting a rural residence of President Vladimir Putin. (Tyler Hicks/The New York Times) By NEIL MacFARQUHAR and IVAN NECHEPURENKO With...