Bill O’Keefe, Catholic Relief Services’ vice president for government relations and advocacy, in December toured C.R.S. and Caritas Internationalis efforts to respond to the continuing refugee crisis in Europe in Greece, Serbia and Macedonia. O’Keefe was astonished by the sight of thousands of people stepping out of rail cars at Europe’s southern borders, walking a half mile toward Serbia and beginning a long journey north to what many hope will be a refuge in Germany and other northern European states. It’s an “overwhelming” spectacle, he said. Though some migration experts had hoped the onset of winter might stem the tide of people in flight, the flow of refugees out of Syria and other zones of suffering in the Middle East shows no signs of letting up. Back in Syria, O’Keefe said, the suffering has only grown worse as a new Russian air offensive joins a Syrian army advance on rebel positions around the war-ruined Aleppo, once prosperous and Syria’s most populous city. Turkish officials worry that a final offensive on Aleppo might drive an additional 300,000 into flight.