LONDON — After weeks of indecision, the European Union voted on Tuesday to distribute 120,000 asylum seekers among member states, a plan meant to display unity in the face of the largest movement of refugees on the Continent since World War II.

Instead, the decision — forced through by a majority vote, over the bitter objections of four eastern members — did as much to underline the bloc’s widening divisions, even over a modest step that barely addresses the crisis.

Nearly half a million migrants and refugees have arrived in Europe this year, according to the United Nations High Commissioner for Refugees, a number that is only expected to rise.

The crisis has tested the limits of Europe’s ability to forge consensus on one of the most divisive issues to confront the union since the fall of Communism. It has set right-wing nationalist and populist politicians against Pan-European humanitarians, who have portrayed the crisis in stark moral terms.