The Tet offensive is in no way comparable to the Ardennes Offensive and certianly not Pearl Harbor. military resolves was not stiffened, morale not raised. The military leaders, for one, actually came to the conclusion that his war was not going right, not going as they had seen it. The president shifted his attention even further from the war, the people more involved in the war(like Clifford and Westmoreland) went even further from the reality of the situation. The troops themselves, they sunk even further into frustrations, stress and unwillingness to stay. Then there is the public. There is a reason why the Tet offensive is called the turning point, the ball just went rolling down and couldn't be stopped anymore, mostly because it was let go off intentionally by some, as the offensive itself didn't make the hill steeper or ball bigger(smaller even). Tet was a wake up call, not to encourage the fighting, like Pearl Harbor and the Ardennes did, but to stop. The fact it was devastating to the VC like you mentioned, is irrelevant. It was intentional even. The North Vietnamese, with Tet, just launched a major attack on the Americans who thought they had it in their hands and the infiltration of the south wasn't all that bad. Now troops knew the infiltration was huge, inivisible, unfightable with conventional means. How would you feel? Doesn't matter they defeated the attacks, that they killed thousands of insurgents, that was not what tet was for. Next to that, more importantly, the Tet offensive of 1968 was followed up by more and more offensives of the same kind, mini-tets. It just got worse and worse for their morale since the leadership started claiming the NVA couldn't do anything like Tet again. Alos the claim that the US won every military engagement with the VC and NVA is false. ground engagements started by the Us for example mostly didn't succeed in their objectives, whilst plenty of engagements initiated by the NVA and VC did, despite heavy losses. Looking only at lossesi s the biggest mistake Johnson, McNamara and Westmoerland did.