The official declined to elaborate but said it was not used when an errant missile landed in NATO-member Poland on Nov. 15, killing two people.Although the U.S. official declined to specify which Russian activity raised the U.S. alarm, there have been publicly acknowledged incidents involving Russian fighting around critical Ukrainian infrastructure.Bursting the dam would send a wall of water flooding settlements below, including towards the strategic regional capital Kherson, which Ukrainian forces recaptured on Nov. 11.Alexander Vershbow, a former U.S. ambassador to Moscow and a former senior Pentagon and NATO official, said the latest deconfliction line was meant to focus on daily operations - as opposed to the more strategic conversations between top officials like Milley and Gerasimov.When the war began, the United States thought Russia might be able to quickly capture Ukrainian territory, trapping American citizens before they had a chance to leave."