GSG-9 was Grenzeshutzguppe - 9 literally Border Troops Group 9 . They were equivalent to our Delta Force. GSG-9 specialized in counter-terrorism and hostage rescue missions. I never came in contact with any that I know about. But generally GSG troops were Federal border guards, GSG-9 was just a specially trained unit. I don't know if they still exist.

Here's some more info on them; http://www.specwarnet.com/europe/gsg9.htm

Thanks,
I'd never read a Clancy novel... this one's fascinating, even some apropos of "warfare modelling" vis a vis our current middle east situations.