"Since its inception, Islam has divided the world into two parts: the "dar al-Islam," or "realm of Islam," which means territory that has already been conquered in the name of Islam, and the "dar al-harb," literally "realm of the sword," meaning territory that has not yet been conquered in the name of Islam.
Once a country has been absorbed into the dar al-Islam it cannot be forfeited or allowed to revert to the dar al-harb. This is how Muslims view Cyprus (and Israel and, for that matter, Andalusia. This is because one of the pillars of Islam is that Muhammad was the last and the greatest of the prophets. Anyone who professes a monotheistic religion that pre-dated Islam (meaning Christians and Jews) may continue to reside in the dar al-Islam, but only as "dhimmi," meaning "protected" persons (protected from death). Dhimmi can never be accorded full political rights, however, since a non-Muslim by definition can never equal a Muslim inside the dar al-Islam.
Muhammad was the greatest and last prophet because all those prophets who came before him (which, in Islam, includes Abraham, Moses, David, Solomon, Jesus, and Mary) failed. Muslims will actually tell you that Moses and Jesus were Muslims. They were sent to deliver the Quran, but the Jews and then Christians mis-transcribed what they received and it came out as the Torah and the New Testament, respectively. They were failed prophets due to the inadequacy of the Jews and Christians. That's why God had to send Muhammad, to finally deliver His true message.
To cut a long story short, this is why the first thing that Muslims do after capturing a city in the name of the dar al-Islam is to turn its pre-Islamic religious sites into mosques. That's what they did with the ka'abah in Mecca, Hagia Sophia in Constantinope and the Temple Mount in Jerusalem, as well as pre-Turkish churches in Nicosia which remain mosques today."
