For John, BLUF: Human patterns are pretty consistent over time. Nothing to see here; just move along.
The magazine Foreign Affairs has an article on "What the Texas Revolution and the Spanish Civil War Reveal About al Qaeda". The author is Mr David Malet, who is a Senior Lecturer in International Relations in the School of Social and Political Sciences at the University of Melbourne. He is also the author of Foreign Fighters: Transnational Identity in Civil Conflicts.
Mr Malet makes the point in his article that the idea of foreign fighters is not new with the current Civil War in Syria, or even the Afghan fight against the Soviet Union.
Unlikely as it may seem, the transnational insurgents in the 1836 Texas Revolution, the 1936–39 Spanish Civil War, and the 1948 Israeli War of Independence inspired the development of the mujahideen in 1980s Afghanistan, from which the jihadi groups of the 2010s directly descend.What is different is the reluctance of nations of origin for these volunteers to take them back. Part of the reason is that nations like Saudi Arabia are not anxious to have their own revolution.
Regards — Cliff