Army Gen. Mark Milley, chairman of the Joint Chiefs of Staff, said his staff tried to get Russia's top-ranking military official Gen. Valery Gerasimov on the phone to discuss the incident with “no success.”Milley didn’t elaborate on the efforts, but the lack of communications raises concerns about high-level U.S.-Russian communications in a crisis.The U.S. and other top leaders now say they believe the strike was probably launched by Ukrainian air defenses to defend against a Russian missile bombardment.“It is unsettling to learn from General Milley that his counterpart was unreachable or not willing to engage when an explosion occurred in Poland.”Milley did talk to his military counterparts in Ukraine and Poland as the governments worked quickly to assess whether the missile that killed two people in Poland had been launched by Russia or Ukraine.Both he and U.S. Defense Secretary Lloyd Austin said that they expect Ukraine to keep fighting through the winter, and the U.S. and its allies will continue to provide more support and weapons.He said the chance of Russia, which currently controls about 20% of Ukraine, overrunning the entire country “is close to zero.” And, he added, the “task of militarily kicking the Russians physically out of Ukraine is a very difficult task."