Max Abrams’ empirical study of terrorism shows that it is ineffective at changing the target government’s policies.

He analyzes 28 Foreign Terrorist Organizations and the outcomes of their campaigns. The terrorist organizations only accomplished 7% of their goals.

Importantly, attacks on civilians were the least successful.

Abrams studied strategic terrorism. This is terrorist attacks against a target government designed to change policies. The 28 organizations attempted to achieve 42 objectives, but were successful only 3 times.

Within the coercion literature, this rate of success is considered extremely low. It is substantially lower, for example, than even the success rate of economic sanctions, which are widely regarded as only minimally effective. The most authoritative study on economic sanctions has found a success rate of 34 percent—nearly five times greater than the success rate of the terrorist groups examined in my study…

Objectives are considered by two types – limited (ie territory) and maximalist (values, ideology). Terrorism only works if the goals are limited. Marxist and Islamist ideological terrorism does not change the values, ideology, or practices of the target government. Some terrorist groups have ambiguous goals or rationales for attacking civilians.

The key variable for terrorist success was a tactical one: target selection. Groups whose attacks on civilian targets outnumbered attacks on military targets systematically
failed to achieve their policy objectives.

The only groups that are successful are those that primarily attack military and diplomatic targets and seek to achieve limited objectives. In other words, the more terrorists behave like classical militaries, they more successful they are.

Attacks against civilians appear to backfire and fail to achieve anything. There are two reasons for this result. First, terrorists tend to be ideologically extreme, uncompromising and often lack concrete motives and goals. Second, terrorists lose political popularity when they attack civilians.

Changing tactics would be hard. Civilians are “soft” targets. Attacking armed military and police targets is considerably more difficult and dangerous. There are fewer potential recruits.

The most successful terrorists? Hezbollah and the Tamil Tigers. Both are part-terrorists, part-guerrillas, and part-political parties. This mixture means they are more formidible threats than most terrorists.