...Simply put, if religion wasn't the rallying cry, it would be something else, probably a form of nationalism. There is nothing unique about Islam other than it survived in its medieval form largely intact to the modern world.
Again, good post from you. I hope you don't mind if I expand on it a bit? This is a copy and paste job from an e-mail I sent someone else before (apologies for the length):
In classical Sunni Islamic theory, there is no 'clergy' along the lines of Catholicism. There are no intermediaries between the faithful and God, no Pope to define the exact rules of practice, and the path to salvation is to be found by simply obeying the commands of Muhammad's successor on earth, the caliph, who is the most suitable candidate for leadership chosen with the consensus of the community.
In practice, the role of caliph lost much of the prestige associated with the early days of Islam, first after it became a hereditary position under the Umayyads and then Abbasids, and then especially after the decline of the central authority of the caliphate during the ninth century, after which a number of autonomous and even explicitly independent powers emerged. This left the Islamic community with a problem - with no real genealogical or institutional links left remaining to the time of Muhammad (although the Shi'a argued otherwise), who was to define the proper practice of Islam?
Into this question stepped the
ulema, the theologian-class of Muslims who assumed the task of establishing some sort of 'orthodox' understanding of the creed (this was becoming even more important since, at this stage some 2-3 centuries since Muhammad, the empire was becoming increasingly Muslim). Two over-lapping trends developed - the Sufi path, whereby salvation was to be achieved either through a direct, personal and spiritual experience of God himself, or if that cannot be achieved, then through a direct link to one who can (a Sufi shaykh/
pir, etc.) - and the Shari'a path, whereby the
ulema classified the standard practice and laws of Islam, with eventually four alternative (though only superficially different) schools of thought on the matter prevailing (these are the four
madhahib - the Hanafi, Maliki, Shafi'i, and Hanbali schools of law).
Naturally enough then, the
ulema came to assume a position of authority in Islam that the majority of Muslims accepted as long as they felt
secure in the knowledge of the supremacy of their civilization (expressed through, for example, the beauty of the Arabic language, and the conquest of non-Muslim lands). In this context, the rise and fall of various sultans, shahs, caliphs, etc. didn't have great significance, The important thing was the maintenance and understanding of the shari'a so that the layman could get into paradise, and if the ruler provided the conditions for that, then his authority was legitimate.
However, the accumulation of centuries of generally unoriginal and repetitive theological treatises, commentaries, and other forms of scholarship produced by the adherents of the four
madhahib created a massive gulf between the average illiterate layman and the original texts upon which the sharia was based - the Qur'an and the
hadith. When the European powers began to encroach upon and eventually conquer much of the Islamic world, many learned Muslims blamed their weakness and relative backwardness on this sense that Muslims had lost touch with the original spirit of Islam, and consequently blamed the
ulema for stifling free enquiry into the original texts and basically acting to preserve their acquired privileges as a unique class within Islamic society.
So by the end of the nineteenth century, there was an anti-
ulema backlash. This coincided with the growth of literacy and the use of print in the Islamic world, which enabled more and more people to directly access the original texts (the Qur'an and
hadith) to understand the practice of Muhammad and the early Muslims (the
salaf), and use their own independent reasoning (
ijtihad) to judge the correct practice of their religion.
This freedom from the conservative
ulema and search for the true spirit of early Islam produced four trends. The lines between them are sometimes blurred, and some movements can be placed across more than one, but it generally holds true IMO.
The first group, the secularists, decided that Western civilization, or at least the Western model of political order, was on the rise and basically superior, and aimed to relegate Islam to the private sphere. The most successful example of this was Ataturk in Turkey, although for almost half a century from the end of WW1 until the 6-day war many Arab countries were generally dominated by 'secular' regimes. However, for obvious historical reasons it was much harder for Arabs to make the clean break with the past that Turkey had done, and Arab Nationalism was always infused with elements of Islamic imagery and rhetoric.
The second group, the 'modernists', believed that by returning to the Qur'an and the
hadith and emulating the prophet, Muslims could reconcile Islam with the reality of Western power, since they believed that Islam, properly understood, already enshrined all the positive aspects of Western civilization, and that there need be no conflict between them. In India, the most famous proponents of this trend were Sir Sayyid Ahmad Khan who founded the Muslim University at Aligarh, and Muhammad Iqbal, the spiritual father of Pakistan, which may have evolved into a leading example of the trend in practice if Jinnah hadn't died so early and the Islamists who had actually rejected the movement for Pakistan hadn't managed to hijack the cause. Another famous proponent was Muhammad Abduh of Egypt, who attempted to reform the Azhar University in Cairo along the lines of a modern European university. He is famous for writing "I went to the West and saw Islam, but no Muslims; I got back to the East and saw Muslims, but not Islam." This trend has probably been the least successful politically, but probably best embodies how most Muslims in the west conduct their lives. A good modern-day example might be Tariq Ramadan, although some have doubts about his genuineness.
The third trend, the 'Islamist', was explicitly anti-Western but revolutionary, and believed that the return to the texts and spirit of Islam was the means to oust the Western powers from Muslim lands and restore the glory of the early Islamic empires. At the same time, they discovered they could utilize Western technology and organization (primarily 'the State') for the good of Islam. This is the trend which produced the Muslim Brotherhood and Jamaat-i Islami, who were influenced in organizational terms by interwar European fascism and sought to seize the state in order to implement a top-down Islamization of society.
These three trends are explicitly
anti-clerical in their disdain for the traditional, conservative
ulema. Hence the lack of officially-earned religious credentials held by members of the Muslim Brotherhood and groups like al-Qaeda. The final trend, what I'll call the 'scriptural', was primarily driven by the reaction of the
ulema to the sudden loss in their prestige and traditional authority. It was deeply conservative and believed the West was best shunned in order for Muslims to maintain their true identity. They tended to retreat into their madrasas and other educational institutions to concentrate on purifying the creed, and often remained apolitical. The best examples would be the Wahhabi trend in Arabia, and the Deoband and Ahl-i Hadis movements in South Asia. The problem for the
ulema in the last century or so has been maintaining their hold over the community. To do this they've had to tread a fine line between the state, which from the mid-twentieth century onwards co-opted them, and the Islamists, whose success and growing prestige undermined their own power. It's no surprise therefore to find them often adopting many of the political positions expounded upon by the Islamists.
Modern-day jihadis represent a coming together of the revolutionary fervor of the Islamists with the deeply conservative literalism of the structuralists - you could say a merger of Sayyid Qutb and Ibn Taymiyyah. But it was by no means inevitable that these two trends would come to dominate the other two, or that they'll continue to do so. The secularist trend failed due to a combination of Western sabotage (most famously in Iran but also in the Arab nationalist states where the Western Cold War bloc supported religious conservatives against the regimes), guilt-by-association (those secular regimes close to the West were tainted by association), the complete failure of the secular regimes to solve any of the region's problems or provide any kind of dignified life for the people, and the rise of Saudi oil money and the Iranian Revolution. And of course various policies in non-Muslim states often help drive recruitment to the jihadi cause.
The modernist trend has suffered from the accusation that its adherents have sought to 'change' Islam in order to have it complement the modern world, and that in doing so they have lost the fundamentals of the faith. Yet I think most Muslims in the West, in the way they live their lives, exemplify this trend, although as yet it has not given rise to a solid political movement. But the idea that Islam inevitably produces groups like al Qaeda and ISIS is nonsense. It requires the coming together of certain trends and historical processes, almost all of which depend on factors beyond Islam.
You absolutely nailed it in the bolded paragraphs.