The Qadiriyya took organized shape only after Abd al-Qadir al-Jilani's death, carried outward from Baghdad by students and, according to tradition, by a large number of his own sons, who established teaching lines in cities across the Islamic world over the following two centuries. Baghdad's catastrophic fall to the Mongols in 1258, which killed much of the city's scholarly class and ended the Abbasid caliphate there, dispersed still more of that early network outward rather than destroying it, and it was this dispersal, rather than any single missionary programme, that gave the order its enduring character: a family of largely independent regional branches, each answering to its own line of shaykhs, rather than a single order governed from one seat.
That structure let the Qadiriyya take root very differently in different regions without contradiction.
In West Africa it became one of several major tariqas competing and coexisting with the Tijaniyya; in South and Southeast Asia it merged in places with older mystical currents already present before Islam's arrival; across the Arabian Peninsula and North Africa it remained closely tied to conventional Sunni legal scholarship, a continuation of al-Jilani's own Hanbali training. No single reform, split or central authority unifies these branches today, and that absence of a centre, unusual for an order of its age and reach, is itself the most consistent thing that can be said about the Qadiriyya as a whole.