Can someone give the name of the fallacy I'm describing?

[Lord MJ]

The fallacy I am describing is one where you try to use one's response to your actions as a justifaction of your original actions.

This fallacy is used in a variety of circumstances ranging from simple conflicts between significant others, to international politics.


Example:

Country A decides to invade country B on the basis that it poses a threat to country A's people. In retalliation to this invasion, Country B detonates a nuclear device in one of country A's cities.

Country A would most likely say that Country B's nuclear strike proves that it is a threat, and therefore it's invasion was justified. (And if Country A was the US, Country B would be reduced to a smoking crater as a result.)

The flaw in this is that Country B's nuclear attack would not have happenned if Country A hadn't invaded them in the first place. Therefore Country A can not use Country B's response to the invasion as a justification of the invasion.

[Alyeska]

Very good logical problem, but I've never heard of this fallacy used like this, so I can't say I know which one it is.

[Darth Wong]

Ethical justifications are not directly addressed by logical fallacies because an ethical justification itself requires the acceptance of a particular ethical system before it can be declared valid or invalid, and logic fallacies are more directly defined than that.

However, if I had to try and pick a fallacy, I'd say it's a "False Cause" fallacy. They're saying that the invasion was caused by something that actually happened after the invasion and would not necessarily have happened without it. The "False Cause" fallacy has many very specific forms for specific commonly-used variants, but not every form of false-cause fallacy has a specific name, so you can just use the general term.

[Shadow WarChief]

Since the cause of the nuclear devastation is incorrectly being attributed to a pre-existing plot rather than a provoked response, I guess I'd call it a False Cause fallacy.........right?

[Lord MJ]

False cause sounds about right.

The simplified version of this is:

I do X because I am afraid of you doing Y, in response to me doing X, you do Y. Since you did Y, me doing X was perfectly justified all along!

I think that regardless of what ethical system you follow, that is fallacious logic, because you can't use an effect to justify a cause of that effect.

[Darth Wong]

False cause sounds about right.

The simplified version of this is:

I do X because I am afraid of you doing Y, in response to me doing X, you do Y. Since you did Y, me doing X was perfectly justified all along!

I think that regardless of what ethical system you follow, that is fallacious logic, because you can't use an effect to justify a cause of that effect.

Yes, most people respond well to the "X vs Y" method of describing fallacies, even if you don't have a formal name to put on it. But your method of describing the fallacy is a bit long-winded. I would put it this way:

"According to you, X caused Y, therefore Y justifies X. By this logic, I am perfectly justified in punching you in the face right now because you'll punch me back".