It should be pointed out that most of these laws were elaborations of basic laws concerning non-Muslims (dhimmis) in the Quran. The Quran does not give much detail about the right conduct with non-Muslims, in principle recognizing the religions of the book and demanding a separate tax for them.
Along with the religion of Islam, the Arabic language and Arab customs spread throughout the empire. A sense of unity grew among many though not all provinces, gradually forming the consciousness of a broadly Arab-Islamic population: something which was recognizably an Islamic world had emerged by the end of the 10th century. Throughout this period, as well as in the following centuries, divisions occurred between Persians and Arabs, and Sunnis and Shiites, and unrest in provinces empowered local rulers at times.
There are a number of historians who see the rule of the Umayyads as responsible for setting up the "dhimmah" to increase taxes from the dhimmis to benefit the Arab Muslim community financially and to discourage conversion. Islam was initially associated with the ethnic identity of the Arabs and required formal association with an Arab tribe and the adoption of the client status of mawali. Governors lodged complaints with the caliph when he enacted laws that made conversion easier, depriving the provinces of revenues.
During the following Abbasid period an enfranchisement was experienced by the mawali and a shift was made in the political conception from that of a primarily Arab empire to one of a Muslim empire and c. 930 a law was enacted that required all bureaucrats of the empire to be Muslims. Both periods were also marked by significant migrations of Arab tribes outwards from the Arabian Peninsula into the new territories.
The expansion of Islam continued in the wake of Turkic conquests of Asia Minor, the Balkans, and the Indian subcontinent. The earlier period also saw the acceleration in the rate of conversions in the Muslim heartland while in the wake of the conquests the newly conquered regions retained significant non-Muslim populations in contrast to the regions where the boundaries of the Muslim world contracted, such as Sicily and Al Andalus, where Muslim populations were expelled or forced to Christianize in short order. The latter period of this phase was marked by the Mongol invasion (particularly the sack of Baghdad in 1258) and after an initial period of persecution, the conversion of these conquerors to Islam.
The Ottoman Empire defended its frontiers initially against threats from several sides: the Safavids on the Eastern side, the Byzantine Empire in the North which vanished with the fall of Constantinople 1453, and the great Catholic powers from the Mediterranean Sea: Spain, the Holy Roman Empire, and Venice with its eastern Mediterranean colonies.
Later, the Ottoman Empire set on to conquer territories from these rivals: Cyprus and other Greek islands (except Crete) were lost by Venice to the Ottomans, and the latter conquered territory up to the Danube basin as far as Hungary. Crete was conquered during the 17th century, but the Ottomans lost Hungary to the Holy Roman Empire, and other parts of Eastern Europe, ending with the Treaty of Carlowitz (1699).
Source: Wikipedia English, 20 February 2011