Marie Henehan presents a systematic study of every roll call vote on foreign policy taken by the Senate between 1897 and 1984. She predicts an increase in Senate activity and disagree- ment on foreign policy after "the emergence of imperialism as a critical issue in 1897, the crisis over involvement in Europe in 1917, the heightened importance of the response to commu- nism in 1947, and the perceived failure of the containment policy in Vietnam between the Tet Offensive in 1968 and the bombing of Cambodia in 1970" (p. 83). She also predicts a gradual decline in activity as the issue is resolved, but increases following major policy failures related to each critical issue.