How Terrorist Groups End

"[Most terrorist groups] ended for one of two reasons: They were penetrated and eliminated by local police and intelligence agencies (40 percent), or they reached a peaceful political accommodation with their government (43 percent)....

"In 10 percent of cases, terrorist groups ended because they achieved victory. Military force led to the end of terrorist groups in 7 percent of cases." RAND Research Brief | How Terrorist Groups End: Implications for Countering al Qa'ida.