WARSAW, Poland—Ukraine’s neighbors in Eastern Europe have ramped up their support for the beleaguered nation in the face of the Kremlin onslaught—closing their airspace to Russian overflights, providing refuge to people fleeing the war, and shipping ammunition. Poland on Friday delivered to Ukraine the first publicly acknowledged military aid since the invasion began, according to the country’s Minister of Defense Mariusz Blaszczak. “A convoy of ammunition we are donating to Ukraine has already reached our neighbors. We stand by the Ukrainians, and show solidarity against Russian aggression,” he said in a tweet. Blaszczak didn’t provide details on the quantity or type of ammunition, but it’s clearly a commodity in dwindling supply in Ukraine, whose forces have mounted staunch resistance and slowed the advance of the Russian war machine. In what some analysts have called his “Spartacus” moment, Ukrainian President Volodymyr Zelensky turned down an offer from the United States of evacuation …