History
Islam spread rapidly into the regions where Muslims are now a majority, until 631 CE - see caliph for the politics that were partially to cease the rapid expansion of Islam at about this time.
Islam was also spread by war and colonialism, particularly of the powerful Ottoman Empire. Nations were conquered, and their inhabitants were forced to convert to Islam, or live as dhimmis, second class citizens.
The Ottoman Empire came to an end in 1918 when Turkey lost control of the bulk of the Arab World, which it had ruled for centuries and in which it had suppressed most of the traditional norms of Islam. Britain and the United States supported Arab independence, but France insisted on retaining control of Lebanon and ultimately Syria. This, plus the status of Kuwait and Palestine, and the later partition of India, remain major sources of global tension to this day. Islam allows oppressed Muslims to practice Jihad, struggle against aggressors.
The 20th century also saw a series of defeats for some Islamist movements, Iran and the now-defunct Taliban regime in Afghanistan being notable exceptions. Elsewhere the rule has been for military rulers, e.g. Suharto, Moammar Qaddafi, Zia, Saddam Hussein, to cynically exploit Islamic imagery and language without following the rules, sometimes implementing weak but spectacular forms of sharia in rural areas to appease peasant supporters.
In Turkey, Pakistan, Algeria and other nations with Islamist parties, these tend to have either no power or they substantially moderate these policies when they participate in government (as in Turkey in 2003 where the government approved a U.S. plan to invade Iraq via Turkey but was over-ruled by the parliament after public pressure from the 94% of Turks opposed to an invasion). Nationalism plays more of a role in decisions to go to war than religious similiarities or differences.
- See also: History of Islam