Quick (Ok, maybe not quick) overview of Wahhabism and its role in radicalization, as presented by the Islamic Supreme Council of America (wiki page). To try to keep this a relatively disinterested response, I decided to only quote a self-proclaimed moderate, progressive association of Muslims to show the discord within the religious community. If you do not trust it, you should judge the source of this information yourself - I'd be happy to hear what you find.
Some cherry-picked quotes:
The origins of nearly all of the 20th century's Islamic extremist movements lie in a new Islamic theology and ideology developed in the 18th and 19th centuries in tribal areas of the eastern Arabian Peninsula. The source of this new stream of thought was a Muslim scholar named Muhammad ibn Abd-al Wahhab, hence the name "Wahhabism." [T]he "Wahhabi" ideology is built on the concept of political enforcement of religious beliefs, thus permitting no differences in faith whatsoever. In "Wahhabi" belief, faith is not necessarily an option; it is sometimes mandated by force. Anyone who did not profess to this new ideology was considered outside of the realm of Islam - an apostate, disbeliever or idolater, thus making the shedding of their blood and confiscation of their wealth permitted.
A struggle ensued between the staunchly orthodox Ottoman Empire and the "Wahhabi" tribes. The Wahhabis were put down until the eventual dismantling of the Ottoman Empire in the 1920s and the dissolution of its influence. Finding a new opportunity among the tribes, Wahhabis were able to reinstate their beliefs and assert their influence on Muslims of the Peninsula. Gradually from 1920 until today, they were very successful in establishing an "accepted" new ideology in Islam whose essential characteristic is extreme views and interpretations, as contrasted with traditional Sunni Islam. Coming under the guise of reform of the religion, the movement gathered momentum in the last three decades with support from a number of wealthy individuals. As it has grown, the movement mutated and splintered, with the eventual outcome that some groups went to the extreme in radicalization of their beliefs.
The Wahhabi mentality asserts that Islam may be reformed by means of the sword. Thus the movement has manifested itself as armed insurrections throughout the world, especially where governments are weak and unable to resist aggression effectively. The extremists who have turned militant declare war against anyone with viewpoints contrary to theirs; thus, declaration of war against a government is commonplace. In Egypt, they oppose their government. Similarly in Jordan, they oppose their government. In Syria, Pakistan, Algeria, and many other countries "Wahhabi-minded" groups oppose their governments as they have begun to do in the Caucasus and Central Asia. The approach of these movements is to infiltrate mosques, Islamic teaching centers, and charitable organizations from where they indoctrinate religiously oriented people with their ideas and methods. They forcefully impose their views on weak societies, in hopes of conquering one and establishing a base for further control. They justify their militant acts and illegal means of financing their cause by claiming to wage a "jihad" for the preservation of Islam.
It is very well known that certain networks have flourished in many countries throughout the world. Small but well-financed militant movements arise, coming against their government and the common people, instigating conflict. The danger lies when an outside government supports such extremist movements under the false impression that this constitutes preserving religious freedom. To understand such movements, one must understand the scope of Islam and the psychology of Muslims, since what we are seeing today is an ideological movement turned militant. It is important to note that the Wahhabi ideology itself is extreme in its interpretation and can turn militant over time.