Since the emergence of the concept of "military operations other than war," it has been used in broad range, and there were abundant related studies and literatures. However when this term is applied in research, it is discovered that there are so many similar concepts in military terminology with different names, or different terms refer to the same phenomena. Therefore, it is worth studying such kind of issues. This study aims to clarify the evolution and relationship among these concepts. We discovered that the thinking and considerations of the U.S. army in applying theses terms are: political implications of these military operations in foreign countries, to match with legal principle for shaping good image of American in terferences, to get rid of awful word of 'war', and to use more soft terms for getting the support from foreign populations and governments.