Gen. Mark Miley, chairman of the Joint Chiefs of Staff, said his staff tried to call Russia’s top military official, Gen. Valery Gerasimov, to discuss the incident without success. Milley did not elaborate on the efforts, but the lack of communication raises concerns about high-level U.S.-Russia communications in a crisis. A strike against Poland, a NATO member, could have risked a larger conflict if it turned out that Russia had launched the strike. The US and other top leaders now say they believe the strike was likely launched by Ukrainian air defenses to defend against a barrage of Russian missiles. But uncertainty swirled for hours. Several US defense officials said it is not unusual for Gerasimov to be unavailable for a call. The lack of communication is troubling, especially given the potential ramifications of the strike, said John Tierney, executive director of the Center for Arms Control and Nonproliferation in Washington. Open lines of communication “are vital if we are to avoid the risk of conflict caused by misunderstanding, miscalculation or error,” Tierney said. “It is troubling to learn from General Milley that his counterpart was unavailable or unwilling to get involved when an explosion occurred in Poland.” Milley spoke with 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 fired from Russia or Ukraine. The discussion came as Milley said Russia’s recent defeat in the key southern city of Kherson and a potential slowdown in military operations over the winter could provide an opportunity for negotiations. “You want to negotiate at a time when you are strong and your opponent is weak,” Milley said at a Pentagon briefing Wednesday. “The Russian military is suffering terribly,” he said, citing heavy losses of Russian tanks, combat vehicles, fighter jets and helicopters. If the fighting slows down, Milley said that could become a “window” for talks on a political solution. Both he and US Defense Secretary Lloyd Austin have said they expect Ukraine to continue fighting through the winter and the US and its allies will continue to provide more support and weapons. And it will be up to Ukraine to determine any negotiation plans. “We have repeatedly said that this will be decided by the Ukrainians and not by us. And we’ll support them for as long as it takes,” said Austin, who was also at the briefing. The missile that landed in Poland on Tuesday was launched during “the biggest wave of missiles we’ve seen since the beginning of the war,” Austin said. On Tuesday, Russia launched up to 100 missiles against Ukraine as Moscow stepped up its airstrikes after heavy ground casualties. Milley said it was unlikely that either side would quickly win a military victory. He said the chance of Russia, which currently controls about 20 percent of Ukraine, overtaking the entire country “is close to zero.” And, he added, “the task of physically expelling the Russians militarily from Ukraine is a very difficult task. And it’s not going to happen in the next two weeks, unless the Russian military collapses completely, which is unlikely.”