Very powerful. If it worked this way, the powers that be would learn other ways of solving our problems besides war very quickly.
My Dad, a long time ago, had an idea for an anti-war movie, wherein everyone who wanted to work for the government sort of volunteered, and if they decided to have a war with someone, only the folks who were at the highest level of government (Congress, the President and his Cabinet) would suffer or die, and it would be a totally random event within a few minutes of the war being declared. One guy would get a fast acting poison injected and die, another would lose the use of an arm, an eye, or both legs, another would catch some horrible, non-communicative disease that would ruin his/her life forever, but no one - not one of them - would escape totally unscathed. All would end up psychologically scarred in some way, either through drugs or via some physical effect.