Waco and Yugoslavia come to mind as two of the more glaring failures to understand the dynamics before starting the shooting. Never fire a warning shot. Deadly force must never be used unless someone is in immediate mortal danger. That means you don't use cruise missiles to 'warn' a foreign power to behave. Shoot to stop a deadly threat, and only if killing your opponent is an acceptable outcome.
Deadly force is justified only in a shoot or be killed situation.
If you can afford to pick and choose targets to avoid hitting objects d'art, you are not yet in a shoot or be killed situation. If you can walk away, you are not in a shoot or be killed situation. Know your target. Be sure that you are shooting at a deadly threat. Don't bomb pharmaceutical plants until you have incontrovertible evidence that they constitute a deadly threat.