One possible way is to have, as the old thread name said, an Islamic Europe and Christian Middle East. Christianity is wiped out of Europe, but Islam is blocked by Persia in the North, which eventually goes Christian (spread from Byzantium, which becomes a mutual alley against Islam which takes Roman North Africa and Palestine.) Eventually Islam dominates Europe (or at least up to the Rhine, Italy and the British Islands). Germany remains Christian, but is weakened from years of war from both Pagans in the East and Muslims in the west and never becomes more then a highly militarized, massive march area. Christianity makes its way to India, maybe forced upon the Indians by a foreign nomad dynasty (Afghans?) which converted through contact with Persia. India remains divided, but Christian gets a foothold in the upper-caste in most of the North so when the foreigners are overthrown the dynasties that replace them are still Christian.
India becomes a loose confederation as well as a Christian bulwark and develops its navy from Princely states, as mentioned before, that excelled at trading. By this point Persia has weakened, been overrun by horse nomads from the North or Arabs from the South or both, the Byzantine Empire continually weakens under attack from the Arab South and West and the Pagan North and East and Germany has pushed East, but still is nothing compared to the massive Islamic Caliphate that encompasses France, Britain, Hispania and Northwest Africa. By the 17th Century India is under one, weak, king with trade posts all along Africa (East, West and South), some areas of the Persian Gulf and Indonesia. The Caliphate has shattered into dozens of warring principalities in Europe, with several large empire in North Africa and the Middle East fighting each other as much as there non-co-religious neighbors.
India seek to open up the closed markets of Europe with the pretext of liberating former Christian lands, but also wish not to anger the powerfully Muslim nations in the Middle East, so they bypass them and launch an invasion of England as a stepping stone to impose their will on the rest of Europe. It is successfully executed and the native Muslim Anglo-Saxons are divided into tributary states, trade posts and outright positions of various Indian nobles and minor kings. Most of the area around London is a direct royal possession of the Indian King and he is officially styled "Emperor of Anglia."
(Double Blind Standpoint) It's all quite unstoppable actually, a country as rich and populated with cultured people who love the sea and are fervently religious Christians should come to dominate Europe.
