This article examines between-group differences in support for military action in the period since the Vietnam War. During the Vietnam War, support for military action was stronger among men, whites, the more educated, the more affluent, and younger persons. In the post-Vietnam era, men have remained consistently more supportive of military action, despite recent changes in gender roles and gender politics. Racial differences have remained strong, but not uniformly so. The gap between whites and nonwhites has been most pronounced in periods of intense partisanship or when military events have sparked a "rally-'round-the-flag" response that affected whites more than nonwhites. Education and income differences have generally followed a similar pattern, although there are signs of a weakening (or even reversal) of differences in attitudes to war on the education variable. Another change in the post-Vietnam era has been the relative decline in support for military action among younger persons. These data are used to explore the diverse causes and meanings of attitudes toward the use of military force and to assess the implications of the social distribution of pro-and antiwar opinion for the conduct of U. S foreign policy and political mobilization on issues of war and peace. Keywords: militarism, public opinion, foreign policy, Vietnam War, Iraq War.