In The Politically Incorrect Guide to Islam (and the Crusades), I discuss the sad case of the Byzantine Emperor John VI Cantacuzenes, who invited the Ottoman Turks into Europe to help him win a dynastic dispute. His invited guests overthrew his Empire about 100 years later, and have stayed in Europe to this day.
There are many other similar examples from Byzantine history. There are also more recent examples of the same phenomenon. The moral of the story is that when playing realpolitik with the mujahedin, remember that they are not likely to discard the jihad ideology of supremacism and expansionism just because you have been kind enough to play ball with them.
From the Times Online, with thanks to Sr. Soph:
MILITIAMEN from an Iranian-backed force were deliberately recruited by Britain to join the new Iraqi security services after Saddam Hussein was overthrown, the Government has admitted.
The sectarian Badr organisation, trained in exile by Iran’s Revolutionary Guards, is suspected of violently pursuing its own agenda after being allowed to enlist in national units.