Many writers have traced the formation of al-Qaeda to the war in Afghanistan in the 80s and 90s, linked with American backing of the the mujahedin. What’s less commonly considered is how those forces matured in Bosnia in the 90s, again with help from the Americans.
In ‘Intelligence and the War in Bosnia’ (published 2002) Professor Cees Wiebes of Amsterdam University complied a report called ‘Intelligence and the War in Bosnia’ in which he details actual alliances between the Pentagon and radical Islamic groups from the Middle East.
America allowed the movement of Islamic fighters into the region but once that genie was out of that bottle it wasn’t going back in. Subsequent events don’t require detailing, but the importance of these watershed years can’t be overstated.
Read what Brendan O’Neill has to say about this over here.