A multitude is more easily governed by humanity and gentleness than by haughtiness and cruelty.~ Machiavelli (surprisingly)
There is no instance of a nation benefitting from prolonged warfare.~ Sun Tzu (perhaps even more surprisingly)
War is good for psychology, in a bottom-line kind of sense. The governments of nations at war and the governments of nations that perceive themselves as threatened are willing to channel research funds to those kinds of projects they think might provide an advantage in conflict. This was so during the World Wars and the Cold War, and it has been so during the so-called War on Terror. Research conducted under these conditions has stimulated the field. Notably, the study of personal (and personnel) assessment has made strides, as has the psychology of leadership and small group behavior. And this is just a small sample of topics from the social psychological end.
Money buys loyalty and commitment. At the dystopic end of the spectrum, we’d have a psychological science that is co-opted by the military. This has happened under totalitarian regimes in historical time, and thus remains a possibility to be mindful of. Recently, the U.S. Army has made a gentler effort to use the services of psychologists in order to prepare personnel for the stress and possible trauma of combat. The ultimate goal is to make a contribution to the protection of combat troops as well as civilians caught in a war zone. If traumatic events occur, the hope is that psychological preparation will reduce the risk of post-traumatic stress disorder. In January of 2011, the American Psychologist dedicated an entire issue to the project of Comprehensive Soldier Fitness (CFS), which is being conducted by psychological services within Army in conjunction with the University of Pennsylvania. The articles featured in the American Psychologist, many showing co-authoring Army personnel in battle fatigues, can at best be regarded as promissory notes, which by itself makes their publication in the flagship journal of the American Psychological Association unusual and noteworthy. Where is the evidence, one might ask, that any of this will work as advertised? To my knowledge, strong evidence of the success of CSF has not been published elsewhere since (see here for a media report).
Psychological science should not lose sight of its broader and deeper mission, which cannot be articulated with respect to national interests. Basic psychological science is concerned with human behavior and experience, whoever these humans might be or wherever they might live. This mission comprises the question of how humans relate to one another in contexts of intergroup conflict. This question, by definition, cannot be subordinated to national interests. When a supra-national perspective is taken, the main question will likely be one about conflict-reduction or peace as opposed to be one about conflict-induction or war.
Stephan Lewandowsky, Werner Stritzke, Alexandra Freund, Klaus Oberauer, and I have organized an alternative special issue for the American Psychologist to showcase and discuss the many contributions psychological science has made to the study and the promotion of peace, and how these contributions can be useful for policy and politics in the future. I refer (and defer) here to a blog post by Stephan, which provides further details.