Ancient and modern

There used to be a major clash of civilizations between the two great monotheistic religions, Christianity and Islam, that are derived from Judaism. This was exemplified by the Muslim invasions of Europe - at the Pyrenees, where Islamic armies were defeated at the battle of Poitiers in 732 by Charles Martel ("the hammer") and the Moors who were finally expelled from Spain in 1492, and outside Vienna in 1683 resulting in the Treaty of Carlowitz in 1699 between the Turkish Empire and the "Holy League" of Europeans. But for these two defeats Europe would long since have become Muslim. The clash was also represented by the counter-invasions of the Crusades.
Now there is a civil invasion by immigration of millions of Muslims into European countries. They come because, like many Africans, there is no work in their countires of origin, that have failed to keep pace with Western development, and because the Western countries need unskilled and some skilled workers to satisfy the needs of their economies. So the Muslims are gradually, by stealth, trying to accomplish what they could not do by force centuries ago. While we must repeat the truism that "not all Muslims are terrorists, but all terrorists are Muslims," we must be aware that most Muslims are in sympathy with the attitudes of the extremists. This is exemplified by the many trials occuring of Muslims in the UK for some relationship with underground, illegal and/or terrorist groups, as well as the use of Muslim facilties, mosques and schools, to distribute anti-Western propaganda. This is the modern onslaught of Islam against the West, but can it be successful where the ancient wars failed?
There is a peculiar resentment among Muslims that they are not predominant in the world. This is a bit like the Communists, whose ideology was supposedly superior to that of materialistic capitalism, even though their system collapsed. Also, Fascism had a superior idology, that involved the killing of all opponents to make a pure world, but luckily that too was defeated. Now the idology of extreme Islam seeks to supplant all other civilizations with their sharia law and Muslim culture. Much of this, while not of specifically religious origin, includes the suppression of women, forcing them to wear all-encompassing clothes, not going out in public alone, not speaking to men in public, etc. Such repressive regimes, as far as the West is concerned, are found in Iran, Saudi Arabia, Sudan, etc.
Now the Pope makes a speech, and very much like the inocuous cartoons published in Denmark, there are demonstrations all around the world, from Egypt to Indonesia and in Pakistan the Parliament passes a unanimous condemnation of the Pope. This is a reversion to the status quo ante, except so far with words and not with guns. But, the Pope was quoting a 600 year old statement, and even if the speech is offensive to Muslims, within the context of a secular society it is totally inocuous, a comment on the historical fact (that Muslims deny) that Islam was spread by "the sword." But, while the Pope may well be right that the use of jihad by Muhammed, spreading Islam by the sword, was an inappropriately violent basis for a religion. However, the Pope seems to forget that Christianty was also spread in a similar way, for example during the Crusades, when many Jews and Muslims were sacrificed to the sword in order to force them to convert to the "one, true faith." The inquisition in Spain was a further typical example of this attitude. In fact, the presence at Regensburg, where the Pope gave his speech, of a notorious concentration camp where Jews were murdered during WWII, was the logical outcome of this Christian attitude. They may not have called it jihad, but the consequences were the same.
So now the big question is whether or not the "clash" between Islam and the West will remain at a slow boil or will it burst out into a full-out war. If it can be subsumed under the rubric of secularism, and can be kept at the level of the war on terrorism, then it can be managed.