What is the difference between war and terrorism?

Question

As the title states, what is the difference between war and terrorism?

Terrorism, as I understand it, has one primary purpose: to destabilize the enemy. Hence, the killing of innocent civilians, while I am sure terrorists get off on that, is not actually the underlying reason for the attack.

But if it is thus an actual strategic attempt to strengthen one's position in an on-going conflict against an enemy, why even call it terrorism? Is it then not simply an act of war, even if it constitutes a war crime? I mean, even a war crime is war. That's why it's called a war crime.

(Note that I know by some definitions, a war is a conflict between countries, but that is not how the word has always been used, even till this day.)

Answer 1

The definition of "terrorism" is not pinned down. This Stack Exchange answer points out that there are many definitions, just within the US legal system alone. These definitions are not even just levels of strictness. They are contradictory in different ways.

Thus, the main reason to choose "terrorism" or "war" is political. Which term, when applied, affects people in the desired way.

War, however, does have a reasonable definition. If we exclude the neologisms like "the war on terror" and "the war on drugs," we find that "war" is a term which has meaning in international law. Importantly, war invokes the Geneva convention (if the states involved uphold it). There are rules, such as those regarding uniforms and the treatment of civilians. Obviously those rules are not sacrosanct (it is famously said that there are no rules in war), but there are rules from the perspective of the international definition of "war."

Answer 2

The chief difference between war and terrorism is the targets.

War works by denying the enemy resources and convincing the enemy that the ultimate result will be defeat. So the enemy surrenders, saving lives on both sides.

Terrorism works by attacking civilian targets and making civilians react. A crackdown on the sources of terrorism is often part of the goal. Because damage to civilians on the terrorists' side often makes more terrorists. They want to enrage people on their own side to join them. In many ways, terrorism is a recruitment strategy. A terrorist strategy makes conflict worse. Both sides are angrier and increasingly likely to retaliate. Fewer people are on the sidelines. Civilians join the war.

As an example, there was the massacre at a black church a few years ago. One of the deliberate hopes of that shooter was to inflame the passions of blacks and encourage counter-attacks. He believed that that would make whites open their eyes to the dangers of racial mixing. Of course, he almost completely failed at that. Fortunately, he didn't think of a smarter strategy, even though others have inadvertently done exactly what he tried to do deliberately.

Answer 3

Indeed, there are numerous definitions for the two terms.
Here's one in a "Explain Me Like I'm Five" style:

War is a conflict between two armed groups A and B. Both attack armed people of its enemy.

Terror is a conflict between groups A and B when an armed group A attacks unarmed people to force B to a certain act (or refrain from it).

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The unarmed people are usually affiliated with B.
A thinks that B will attempt to avoid dishonor, humiliation, public unrest, protests, economic degradation, or other negative effects and will act according to A's will.

But if it is thus an actual strategic attempt […] why even call it terrorism?

Because the B's counteraction against terror is essentially different from actions in a war. The terror usually occurs in the deep rear, quite often in a totally peace time.