"The world's two biggest religions, Christianity and Hinduism, would heavily influence the course of World History during the 2nd Millenium, with them both continuing to remain the two most followed religions as of the present day."
The first sentence of a textbook for history, by Mahmad Idrissou. In this world, Islam
did and does exist, but instead of successfully conquering from Makkah and Medina, the new "cult" was chased down and persecuted by Christians and pre-Muslim Arabs (Zoroastrians etc.) alike. A significant number of followers could be gained in Egypt and other parts of North Africa, but these states remained Christian or were soon forcibly reconquered.
Persia was conquered and vassalised by a much greater and longer-lasting Chalukya Empire in 823-831, finally spreading Hinduism to the Middle East. Egypt was the next state o fall to the Chola-Persian onslaught, giving rise to
Nilotic Hinduism, Nile Hinduism or
Neo-Gangaism in 927
- bascially still Hinduism, butprojecting the sacred qualities of the Ganga river onto the Nile. The few remaining Muslims, persecuted by Nile Hinduist Egypt and the Christian exarchates etc. alike, did not see respite as Hinduism - albeit briefly - spread west to Morocco and Mauritania, and into southern Spain and Portugal (Tacha Kingdom, 981-1153). In conflicts with Christianity, Nile Hinduist explorers (and some following subsets of it, like Tacha Hinduism focusing on the Tejo river) explored and found the New World, and were eager to colonise the areas where they landed in OTL Georgia and Florida.
Colonies and the influence of Hinduism grew and grew and grew, despite the original Chalukya Empire falling into civil war in 1240 and the Rashtrashya Dynasty rising to unite India again in 1269. Many of the vassals went their own way, but from Egypt westwards, Nile Hinduism was firmly ingrained - and over time, as the colonies developed,
Vishishipa Hinduism based around the Mississippi River developed (first written about in 1307). In the 1220s, Muslims for the first time managed to build a stable nation south of the Senegal River.
Christian states were the others to develop major colonies, and conflicts - hot and cold, dynamic and static - between Christian and Hindu states continue to this day. Despite all attempts by Christian scholars and rulers to use distinctions between the sacred rivers as dividing lines, Hindu scholars (and most experts) classify the different river-based offshoots as one large Hinduism, divided up into Ganges Hinduism, Nile Hinduism, Vishishipa Hinduism, Mekong Hinduism, Yangsha Hinduism, Kshatra Hinduism (based on the Amaon) and "Lake Hinduism" or "Majji"- the latter sometimes classified as its own religion.
EDIT (after seeing - and thus heavily inspired by - the above post): Although Christianity and the several river-based types of Hinduism are the main religions - with Hinduism dominating even over Christianity - several other religions are followed too: Judaism has lasted through the times, as has Islam (but some consider it a Hinduist branch/sect/cult in Western Africa). Buddhism in Southeast Asia still has followers, but most importantly, Scandinavia and a majority of peoples in the Baltic and *Russia have remained polytheists. The same applies to many indigenous peoples of Central Africa, the Kshatra region (i.e. OTL Amazon rainforests),...
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