If I knew this first hand, and I knew there was no chance to avert the attack by non-millitary means, then your scenario works. But, realistically, the question should be: If your leaders TELL YOU a nation is about to attack, and so they MUST attack first, do you support the decision?

I say the evidence says leaders cannot be trusted to tell the truth to the public. Also, if you have not yet been attacked, you cannot be certain you will be – intelligence agencies get things wrong, and leaders change theit minds (and a little phone call that says “hey, we know you’re about to attack, and we’ve got a retaliatory strike ready, I’d reccommend against it” might help that process along, particularly in the case ofa country with the millitary power of the US).

Would you imprison someone for a crime they had not yet committed, because you KNEW they would? Unless you can see the future, that’s not a reasonable position.