After the Mongols finished off the Islamic empire in the 13th century, the region of Arabia, the Mamluks, who were former Turkish slaves, set up their caliphate in Cairo, controlling the lands of Egypt, Syria and Palestine. The Mamluks actually repelled further attempts at expanding the Mongol empire from Bagdad, and they took control of the vital parts of Arabia, namely the Holy Cities of Mecca and Medina.
Interestingly enough, the Muslims did defeat the Mongols in a way, in that the Mongols had converted to Islam. However the Islamic empire ceased to exist and the area wouldn’t recover for centuries.
After the defeat of the Franks (crusades), maritime trade flourished in the Mamluk empire. The port of Jeddah in the Red Sea particularly. Contact with peoples from around the world became more and more frequent, especially ships from China.
The animosity because of the Crusades, and the European issues with the Ottoman Empire caused Europeans to try to find a way to India that didn’t involve going through the Red Sea. This was the big push to find the route around the southern tip of Africa.
The Portuguese, with expeditions of Dias and Vasco de Gama, found that route, and trade with India and conquest of the east Indies began. The Portuguese and Egyptians fought a lot, and Portuguese military ships scuttled many Indian trading ships. The Egyptians engaged the Portuguese many times, and the Portuguese responded by sacking Arabian trading ports.
The Ottoman Empire began about when the Mongols captured Baghdad, but gradually expanded out over Anatolia (modern Turkey) and ended the Mamluk empire in 1517. By extension, the Ottomans gained control over the holy lands. Not content to rule by hands off taxation and representatives, they pushed into Arabia and took direct control of ports in the Red Sea. The Ottomans continued the tradition of the Sharifs controlling of Mecca, but they often appointed the Sharif, as opposed to hereditary succession.
Later, the Ottomans began to take control of eastern regions of Arabia, capturing Hasa and appointing regional governors there. In 1669, local clans clashed with imperial forces and drove them out.
The tribes of central and eastern Arabia have always been independent minded and resistant to foreign control, and the Ottomans never held significant sway in that region.
The central region, or the Najd, remained in disarray throughout this period, kept in chaos by blood feuds, raiding, tribal warfare, shifting alliances, droughts, famines, and plagues of locusts (you think I’m kidding). In the early 1500s, the tribes of three towns vied for dominance of the area: Diriya, Uyaina, and Hufuf.
In Diriya, a fractured line of family succession for the emir-ship of the city (Father murdered, son murdered by cousin, cousin murdered by son, son murdered by another cousin, etc…) led to the emir named Muhammad ibn Miqrin, who had a son named Saud, who came to power 1720 and began the house of Saud, which would carry on to the present day.
In response to the decay of the religion of Islam, in which saint-worship, belief in charms, offerings, superstitions, and the animist belief in the powers of trees, rocks, tombs and the like, all crept into the belief systems of many Arabians. A strong religious movement started in the Najd by the son of respected theologians, Muhammad ibn Abd al-Wahhab. His teachings caught on, and he was accepted by the Emir of Uyaina. His teachings were conservative, but they were also fairly harsh, in the realm of penalties for disobeying the strict edicts of the sect. Word got around, and he was eventually driven from Uyaina to Diriya, where he was accepted by Muhammad ibn Saud and offered protection.The sect of Islam became known as Wahhabism, which is the radical sect that bred Ossama bin Laden.