What are the types of targets and tactics used by terrorist and organized crime organizations, and why?

Terrorist groups pick highly visible targets that will cause the most damage with the least expense to their organizations. These targets are often not guarded, such as open markets in Baghdad. The ultimate goal of terrorism is to affect the politics of a country. Attacks against foreign embassies are meant to force a country out of a region or to denounce a nation's political and/or military action abroad. One reason for the September 11 terrorist attacks was Al-Qaeda's protest against American involvement in the Middle East. Terrorists have struck in Moscow to protest Russian involvement in Chechnya. The Irish Republican Army fought a long-running battle using terrorism in order to drive the British out of the country. Sometimes terrorists resort to assassination, such as when Gavrilo Princip killed Francis Ferdinand, thus starting World War I.
Organized crime uses violence as a way to intimidate rivals and to claim territory. The St. Valentines Day Massacre in Chicago is still one of the most famous uses of violence in organized crime. Several gang leaders were assassinated in this act that was meant to look like a police sting operation. Violence is also a tool used to intimidate law enforcement officials, as thousands of police officers have died fighting organized drug cartels.