I was interested this morning to hear that the media has finally picked up on one of the reasons for the Madrid 3/11 bombings. Spain was once part of the Dar al-Islam, or House of Islam, when it was under Moorish rule from the early 700s to 1492 (remember Charlton Heston in El Cid?). The peninsula was known as al-Andalus, a name which lives on today in the name of the province Andalucia.
The radical (and some would claim this is the Wahabbi) Islamic world view behind much of the current terrorism divides the world into two: the Dar al-Islam, where muslim governments exert Sharia law, and the Dar al-Harb, or the House of War - land yet to be conquered by Islam.
A central tenet of Islam holds that land once under the Dar al-Islam must never be ceded back to the Dar al-Harb. All effort is to be put into regaining lost lands, no matter how long it takes: i.e. Israel/Palestine, Afghanistan, Iraq and Spain. The most extreme view holds that most of what the West would consider muslim governments are in fact in Dar al-Harb, because these governments do not enforce strict Sharia: Jordan, Syria, Egypt - and even Saudi Arabia itself, home of most Wahabbis. This is partly the reasoning behind the violence in these countries, and unfortunately there is no long-term solution, because compromise is explicitly prohibited.
More moderate muslim philosophers have added other houses: the Dar al-Amn, or House of Safety, describing muslims living under non-muslim (but tolerant) Western governments (also called Dar al-Shahadah, the House of Testimony); and the Dar al-Dawa, or House of Invitation, describing lands where Islam is newly arrived, but not yet the law of the land.
We might not like being labeled as "Crusaders," but we will eventually have that role forced upon us as the Dar al-Islam achieves its long-term objective, the elimination of the Dar al-Harb.
Perhaps we should send missionaries to convert them? Oh no, wait - that's their plan.