Islam is a monotheistic religion based upon the teachings of Muhammad, a 7th century Arab religious and political figure. It is the second-largest religion in the world. Linguistically, "Islam" means to submit, and refers to the submission or total surrender of one's self to God. Thus, a Muslim is "one who submits to God".
Muslims believe that God revealed the Qu'ran to Muhammad and that Muhammad is God's final prophet. Muslims consider the Qu'ran and the traditions of Muhammad in the Sunnah to be the fundamental sources of Islam. Like Judaism and Christianity, Islam is an Abrahamic religion. Islam has historically recognized the Abrahamic roots all three religions share and protected Jews and Christians living within their countries, however, several Muslim countries have had increases in anti-Semitism due to in part the existence of Israel. Christian-Islamic relations have also suffered due in part to Christian blame of 9/11 on Islam.
Christians in Muslim kingdoms were allowed to quietly practice their religion, but public displays were prevented. Moreover, Christians were taxed by their governments. Thus, the Christian population of Islamic kingdoms continued to decline as many saw converting to Islam as the easiest course.
Islam was disdainful of the practice of Christianity that had arisen in Northern Europe, which held that a religious leader named Henri was the Second Son of God. A central tenet of Islam held that Muhammad was God's last prophet. While Muslims accepted Jesus as a great prophet (although not as the Son of God), they rejected Henri as a creature of Satan.
Muslims frequently traveled in Christian kingdoms to trade. While Christian kingdoms were suspicious of Muslims, they did not persecute them, knowing that they were not strong enough to stand against the Muslim kingdoms. For this reason, the JewishKlein family disguised themselves as Muslim Arabs while traveling in the Kingdom of Versailles--Jews were actively persecuted by both Christians and Muslims.
Islam finally succeeded in destroying the State of Israel in the 21st century. Most Jews in Palestinian domains were content to live under Muslim rule. However the Second Irgun sought to drive the Muslims out by force and restore the Jewish State.
The entire Islamic world (with the exception of the former Dutch East Indies, conquered by Japan) was conquered by the Race. Adherents of Islam, including Ruhollah Khomeini, tended to be militantly opposed to the Race's presence on Earth, especially when FleetlordAtvar attempted to impose the cult of emperor-worship on his Tosevite subjects. In Arab countries, Islam proved a stronger and more effective ideology uniting people against the Race than Arab Nationalism, which was the dominant ideology previous to the Race's landing. For their part, members of the Race (erroneously) perceived Islam as one of the religions which imagined God as a large human, which seemed an utterly ridiculous idea.