Although previous studies have examined U.S. public support for the use of military force in particular historical cases, and have even made limited comparisons among cases, a full comparison of a large number of historical episodes in which the United States contemplated, threatened, or actually used military force has been missing. An analysis of U.S. public support for the use of military force in twenty-two historical episodes from the early 1980s through the Iraq war and occupation (2003-05) underscores the continuing relevance of Bruce Jentleson's principal policy objectives framework: the objective for which military force is used is an important determinant of the base level of public support. The U.S. public supports restraining aggressive adversaries, but it is leery of involvement in civil-war situations. Although the objective of the mission strongly conditions this base level of support, the public is also sensitive to the relative risk of different military actions; to the prospect of civilian or military casualties; to multilateral participation in the mission; and to the likelihood of success or failure of the mission. These results suggest that support for U.S. military involvement in Iraq is unlikely to increase; indeed, given the ongoing civil strife in Iraq, continuing casualties, and substantial disagreement about the prospects for success, the public's support is likely to remain low or even decline.