The number of international terrorist incidents in 1985 was 25-percent greater than in 1984, which saw a 20-percent increase over terrorism in 1983. International terrorism is likely to remain a prominent international political factor. For the United States, it will continue to be more external than internal. Open societies will remain principal terrorist targets, often with the support of various states. At least 100 planned terrorist attacks targeting U.S. citizens and facilities abroad during the past year have been prevented through improved intelligence, stronger security, and cooperation from other governments. The U.S. Anti-Terrorism Assistance Program, which has been operating for 2 years, is improving bilateral cooperation with many European, Middle Eastern, and Latin American countries. It also trains foreign civilian law enforcement agencies to combat terrorism in various fields. State-supported terrorism may be challenged under the doctrine of self-defense, using force proportionate to a clearly documented threat when no other means has been effective.