For much of American history, political leaders have stood by a principle that "politics stops at the water's edge." While political disagreements about domestic policies are seen as inevitable and even healthy, there has been a tradition of trying to avoid partisan disagreements over foreign policy. As a result, intense disagreements over foreign affairs have rarely been the focus of presidential election campaigns. This will not be the case in the upcoming 2008 presidential election. As the presidential election draws near, students will be bombarded with a barrage of political rhetoric emanating from debates and the media coverage. For this reason, now is an opportune time to support students in understanding the major issue in this election, foreign policy, by looking to the past. College courses examining the United States presidency and foreign policy can span a semester. To narrow the scope of study, educators can build a framework that allows students to compare what has happened with what is happening now by focusing on critical junctures and defining moments in foreign policy. This article will use primary source and other documents to examine two defining moments chosen from twentieth century presidencies to illuminate the complex issues surrounding foreign affairs: President Wilson's support for the League of Nations and President Roosevelt's agreement with Churchill and Stalin at the Yalta Conference. Looking through a historical lens will help students develop critical thinking skills that they can also apply to the analysis of the policies of the presidential candidates in the upcoming election. (Contains 7 notes.)