Player, for me to answer that question, please define what you would accept as “defense:”
- Defense against actual attack against US territory by conventional, unconventional, nuclear, radiological, chemical, biological, and/or cyber forces?
- Defense against actual attack against US allies and/or interests by same?
- Defense against actual attack against friendly or neutral peoples or nations that request US assistance?
- Defense against the imminent threat of attack by same (of course, this assumes you've sufficient intel assets in place to detect this)?
- Defense against actual or imminent proxy attack - do you consider the defense to be against the proxy or the sponsoring power, or both?
Now, if we also consider non-direct population damage - economic, infrastucture, resources, food/water supply, etc., what level of damage justifies a war of defense? Now consider the consequential indirect loss of life. How many lives lost indirectly (through, for example, patients dying because hospitals were disabled) would justify a war of defense?
And, while we’re at it, should we feel justified going to war, what should our goal be? To remove the ability to attack the US, or, if something less, what would that be?
Answer these questions, and I’ll be able to give you an example, if it exists.