Andean history up until July 1532 is more or less as history went IOTL up until that point. From there on go the divergences.
-1532: After the Battle of Cajamarca which resulted in the defeat of Huascar, an outbreak of smallpox occurred amongst the Inca army, resulting in Atahualpa contracting the disease. Amazingly, he survived the disease despite severe scarring and would never be afflicted with smallpox for the rest of his life.
-The ravaging of the Andean population by Old World disease led to an enormous amount of death and severely shook the Inca Empire. However, by the 1540s, the spreading of the disease had died down, although the disease would flare consistently and haunt the Inca up until the spreading of inoculation via contact with the Muslim world, and ultimately, by the invention of the smallpox vaccine. Ironically, the Inca Empire was the first country in the world to wipe out smallpox within its borders through rigorous vaccination campaigns in the XXth century.
-1530s and 40s: Inca Empire carries on shakily, but solidly.
-1534: Huscar names his son Awkipuma his successor and has a daughter named Sisa Killasumaq(meaning: flower beautiful like the moon)
-1546: Muslim explorers in service of Al-Andalus return from what is IOTL Colombia in the 1540s with news of a great pagan empire on the mountains to the governor of the Andalusian colony of XXXX.
-1547: Expedition is sent out to convert the Inca to Islam. The expedition was headed by Malik al-Harari, the young grandson of a Jewish refugee from France who converted to Islam. The expedition contained 75 soldiers, all armed with guns and on mount. al-Harari spoke Andalusian Arabic, Hebrew, and Latin fluently.
-1548: The mission arrives in Quito in peace, and Atahualpa arrives with 5,000 men(the amount of men he can draft for his armies has been severely reduced) within two weeks to meet with the Muslim emissaries. By the time of arrival, the mission had acquired several dozen converts out of a city of 50,000.
The expedition was friendly and open at first, with the Sapa Inca offering a gift of Incan textiles and food, that the Muslims took as a tribute. However, when the Sapa Inca scoffed at the idea of converting to what he understood to be a religion that worshiped a rock, the atmosphere quickly turned furious. The missionaries left, while the Sapa Inca remained indignant, but al-Harari vowed to return and to convert these people to Islam.
-1550: A second expedition once again headed by al-Harari arrived to Quito. By the time of return, there were several hundred converts in what we now know as Ecuador, and was beginning to spread southwards towards the former lands of the Chimu.
This expedition was aided this time by a few converted Quechuas that would serve as translators between the two groups. Negotiations and explanations proceeded apace rapidly. The Inca agreed to convert to Islam, but refused to bow towards Mecca, angering the Muslims and earning their mistrust. At the same time, miscommunication between Cuzco and Quito resulted in a rise of anger and suspicion towards the Sapa Inca in his court for converting. How dare he abandon the very functional apparatus of the state! This can be explained by historical accounts stating the Atahualpa believed that he would be the equal of Muhammad, which is why he agreed to convert. Regardless, this quickly culminated in a rebellion in Cuzco within a month of his conversion lead by his own heir, Awkipuma, against the already aging Sapa Inca who was located in Quito finishing negotiations.
Seeing an opportunity to gain the Sapa Inca's good will, al-Harari offered to aid the Sapa Inca in putting down the rebellion. Quickly agreeing, the Inca's 5000 men and 125 Muslim warriors on horseback quickly traveled south, where they confronted the rebellious nobles and the heir apparent. No attempts at negotiation were made, and the battle commenced immediately, fifty-five miles from Cuzco at Ollantaytambo. The Battle of Ollantaytambo would be the most decisive event in Incan history due to its outcome.
Facing the army of 5,100 men was an army nearly triple its size and composed of all of the rebellious nobles who decried Atahualpa's conversion. The battle took place in a valley and would ultimately result in a routing and complete elimination of the army down to a man. The battle commenced with the charging of the rebel army's levy of men head on towards the Muslim position at the mouth of the valley with elevated hills all around them. The charge was quickly destroyed when a loud bang noise was heard, and the first men running fell to the ground, dead. A larger explosion was head immediately afterwards, and large explosions occurred in the middle of the rebel army's main body.
Never having seen firearms before, the rebels acted predictably and fell into chaos and even infighting. Al-Harari's battle plan had succeeded; the Inca had more or less won. The Sapa Inca's army advanced and systematically cut a swath through the disintegrating army to Awkipuma's camp, where he was captured and shipped back towards the Inca's camp. Atahualpa took pity on his son and allowed him to be led with his dignity intact. This would be the most fatal mistake Atahualpa would ever make and be the beginning of the end of purely Quechuan rule. Upon turning his back, Awkipuma lunged with an obsidian knife. Before anyone could react, it was too late, and Atahualpa was bleeding out.
According to historical accounts, Atahualpa reached out to al-Harari before falling, dead to the world. What happens next is unclear, but what is known as fact is that al-Harari took charge and finished off the remnants of the rebel army and took Awkipuma's head with him. Cuzco, defenseless after having its garrison force used as the backbone of the rebel army, laid the gates before al-Harari and his victorious army. What occurred next again continues to remain unclear, but what is fact is that by the end of the day, Al-Harari had installed himself as Sapa Inca of Tawantinsuya, that he had taken Sisa Killasumaq, Atahualpa's 16 year old daughter as his first wife, and that any son of the Inca that still remained alive and in opposition to his rule was dead, and that the construction of Cuzco's first, biggest, and grandest mosque was already underway.
From 1550 onwards, Tawantinsuya would go in a new direction more radically different than the past, in a scale even incomparable to Pachacuti's conquests or the Incan Civil War.
TO BE CONTINUED.