The rise of Islam blocked Europe’s eastern trade routes and shaped the Crusades

Evidence

A key factor in this was that after the seventh century AD, “sea-routes and land-routes alike were barred by the meteoric rise of Islam, which interposed its iron curtain between West and East” (Latham 1958, 8). It was Arab middlemen who brought eastern goods to the European seaports of the Mediterranean and Black Sea to sell. The Crusades (1095–1291) were the long, and for a time unsuccessful, struggle of Christian Europe to roll back this “infidel threat.” — Stuart Hall, Essential Essays, Volume 2, 558