Agreed, there were a number of reasons that led up to the War of 1812. Britain's efforts to blockade Napoleon's empire in Europe led directly to friction with the United States at that time...and that was really, I think, inevitable under the circumstances. I think the Americans had a right to be upset about the British actions at sea, but I also think they used it as an excuse to do what they wanted to do anyway...invade and annex British North America...and they figured the British were too involved in Europe to be able to stop them. They were overly optimistic in that regard.

The British defeat at New Orleans was due to the British commander very foolishly hurling his men across open ground at a very well prepared American defensive position...and they got slaughtered. He was obviously overly optimistic too. :-)

What you had there was some bad miscalculations on both sides. Nobody won that war in any decisive way, it was effectively a draw. It secured no real gains for either side. I don't think either of them decided "We can't win." they just both decided it wasn't worth continuing with the thing...and they were absolutely right about that. It was a war that never should have been fought (similar to most wars in that regard).

Here's one side effect that I'd say both sides did gain, though: Useful combat experience for their navies. The Americans had designed and built the world's most effective frigates by far at that time and it gave the British quite a shock when they lost some frigate-to-frigate actions with the American ships. This was a valuable wake-up call for the British Navy which had grown complacent and used to defeating any and all opponents on almost every occasion. Captain Broke of the Shannon did defeat the American ship Chesapeake, due to the fact that he had drilled his men to an absolute peak of efficiency for some time prior to that action, and that time it was the American commander who was complacent and got a surprise. It was said to be the fiercest engagement between 2 lone ships of that entire era.

Anway, as you said, "you can't can't win a battle if you think you can't win". Agreed. At least, you're sure not likely to win it...

But you can lose a battle even when you think you can win it...and if the battle is a very dumb idea in the first place then why should people not criticize the decisions that led to it?

The difference here is, you think attacking Iraq was justified, and I don't think so. I will not support a war that I think is unjustified aggression, and I will not be called a "defeatist" for objecting to a war that I am opposed to on principle. Nor should others be called defeatists for doing that. They would be defeatists if they thought that their own ideals were not worth fighting for...not because they believe your ideals are not worth fighting for.