Jumping off some of Hannah Arendt's observations about Vietnam, Dave Meyer has an excellent post about Iraq and war as a "signaling" strategy:
The official obsession with image developed over time in the Vietnam era. With Iraq, it was central from the beginning. Before the war, Andy Card told Elisabeth Bumiller that "from a marketing point of view, you don't introduce new products in August." Tom Friedman thought invading Iraq would communicate a useful "Suck. On. This." Jonah Goldberg glowingly attributed to Michael Ledeen the idea that "every ten years or so, the United States needs to pick up some small crappy little country and throw it against the wall, just to show the world we mean business." There are countless examples, from high government officials to low pundits, of endorsements of Iraq for the message it would send, as an easy way to dispel the myth of American weakness. The Iraq war is a multi-trillion dollar public relations campaign, aimed at persuading hostile forces of our "strength."
To add some further context and specificity, I point out in Heads in the Sand that the Bush administration wanted to simultaneously get more rigorous about cracking down on nuclear activities in unfriendly states and less scrupulous about U.S. compliance with the multilateral non-proliferation regime. Consequently, they wanted regime change in Iraq not just for its own sake, but also to "send a message" to would be proliferators in Iran, North Korea, and elsewhere.
As Dave points out, however, among many other problems with using war as a signaling device in this way, it has a very strong tendency to undermine democratic norms at home -- "Effective marketing requires message discipline; in the context of a public relations war, there is a real sense in which dissent muddles the message." This is especially true in the modern world where it's essentially impossible to segment your message. In the past, it might have been viable for an administration to communicate one message, in foreign language, via the foreign press, to foreigners while allowing for a more muddled national dialogue in the domestic press and vernacular. But those days are gone, and today message discipline requires totally discipline.
I might also add that the problems here are a two-way street. Attempting this sort of messaging strategy gets you involved in illegal domestic propaganda but unless you actually succeed in snuffing out democracy (and perhaps not even then) you're going to find it essentially impossible to communicate an unambiguous message abroad.
U.S. Air Force photo by Staff Sgt. Samuel Bendet