From the the 16th century onwards, Islam was in retreat and falling under the domination of an expanding Europe. It started with the reconquest of Russia and Spain. Western Europeans established a growing hegemony in Southeast, South and Southwest Asia. This virtual pincers movement of Russia from the north and Western Europe from the south went unnoticed for a long time because of the incredible military might of the Ottoman, Persian and Mughal empires. But eventually these empires weakened and succumbed to the European and Russian onslaughts.
After World War II and the dismantling of the European colonial empires, most of the areas which had been part of the Islamic Empire were given their independence. But the partitioning of these regions largely ignored ethnic divisions, a problem which remains unsolved today.