Instances of Use of United States Armed Forces Abroad, 1798-2014. Barbara Salazar Torreon, Information Research Specialist, September 15, 2014.

“The following list reviews hundreds of instances in which the United States has used military forces abroad in situations of military conflict or potential conflict to protect U.S. citizens or promote U.S. interests. The list does not include covert actions or numerous instances in which U.S. forces have been stationed abroad since World War II in occupation forces or for participation in mutual security organizations, base agreements, or routine military assistance or training operations. Because of differing judgments over the actions to be included, other lists may include more or fewer instances. The instances vary greatly in size of operation, legal authorization, and significance. The number of troops involved ranges from a few sailors or Marines landed to protect American lives and property to hundreds of thousands in Korea and Vietnam and millions in World War II. Some actions were of short duration and some lasted a number of years. In some instances a military officer acted without authorization; some actions were conducted solely under the President’s powers as Chief Executive or Commander in Chief; other instances were authorized by Congress in some fashion. In 11 separate cases (listed in bold-face type) the United States formally declared war against foreign nations. For most of the instances listed, however, the status of the action under domestic or international law has not been addressed. Most instances listed since 1980 are summaries of U.S. military deployments reported to Congress by the President as a result of the War Powers Resolution. Several of these presidential reports are summaries of activities related to an on-going operation previously reported. Note that inclusion in this list does  not connote either legality or level of significance of the instance described. This report covers uses of U.S. military force abroad from 1798 through 2014. It will be revised as circumstances warrant.”