Germany, overwhelmed by an unprecedented wave of refugees, reintroduced controls along its border with Austria, in a desperate attempt to defuse a crisis that is testing the limits of European solidarity. The surprise move, announced late Sunday afternoon by Interior Minister Thomas de Mazière, marks a significant escalation of the crisis. Berlin has effectively suspended the EU’s open borders treaty, which many view as the embodiment of European integration. “Germany has shown a willingness to help, but this must not be overstretched,” de Mazière said in a statement to the press, adding that the decision was made in consultation with...