Unpacking how the best chance in years to reform Europe’s migration rules would affect the Continent.

Late on Thursday, 21 EU countries pushed through what they hailed as a “historic” agreement to reshape — for the first time in years — how the continent processes and relocates asylum seekers.

If the pact can get through final negotiations with the European Parliament, it may change the face of European migration. Fights and changes are inevitable, and no one is sure how the policy itself would play out.