Can peace be achieved through war? Of course it can. Every war has been followed by a peace of some sort. It's not that unusual for aggressors to be defeated through war, thus ushering in a new era of peace and freedom -- or at least relatively more peace and freedom than before. At the same time, though, it's also not that unusual for wars to lead to eras of greater repression and brutality. Perhaps the more relevant question is whether peace can be imposed through war -- whether war can be used as an effective means for imposing peace, democracy, justice, etc.
That's the question which faces America today because the Bush administration has chosen to try to impose democracy in the Middle East through force of arms. Muslims who try to achieve their goals through killing and brutality are chastised as barbaric. Those goals include the "true" freedom under Islam and Islamic government. America's efforts to achieve its goals through killing and actions which the victims regard as "brutal" is only acting out of an altruistic desire to spread freedom.
The parallels between the two are not exact, but they are striking. Both regard the other as using violence to impose repression and immorality; both see themselves as the bearers of civilization, freedom, and order which justifies the need to use a bit of violence to promote. It's hard for Americans to see this because Americans tend to have a naive sense of innocence about themselves -- they feel that they are only ever acting for the sake of helping others, never out of self-interest, and this leads to very strong negative reactions when those actions aren't received (or perceived) in just that manner.
Even if it could be demonstrated that Americans were absolutely correct and just, it would help if they could see themselves as others see them and their international policies. It might instill a bit of humility, something that goes well even with the pursuit of truth. Of course, in cases where America is wrong, that humility would be even more important.
This image is based on a World War II poster saying that "It Can Happen Here," so people need to keep producing war materiel in the factories in order to keep it from happening.