Late in 1918, Theodore Roosevelt, the 26th president of the United States, was preparing a return to presidential politics, believing that he could gain the Republican nomination for the 1920 election. But on January 6, 1919, he died suddenly and unexpectedly in his sleep.

At that moment the incumbent Democratic president, Woodrow Wilson, was in Paris, awaiting the preliminary meetings of the peace conference that would bring a negotiated end to the First World War.

Roosevelt and Wilson could not have been more different in terms of personality and political persuasion: indefatigable macho realist meets professorial Calvinist idealist. Their relationship was inevitably difficult. They had faced each other as contenders for the presidency in 1912, and Wilson had won. In the 1916 election Roosevelt was again disappointed when the support he gave to the Republican candidate was not enough to defeat Wilson.

All things being equal they would have faced each other again in the next election. But it was not to be for either man. In Colorado in September 1919 Wilson suffered a nervous collapse. He was in the midst of a speaking tour to gather support for his beloved League of Nations and the Treaty of Versailles, both of which awaited U.S. ratification. On his return to Washington, D.C., the president had a paralyzing stroke from which he never recovered sufficiently to run for reelection.

In matters of foreign policy, Roosevelt and Wilson did share some perspectives. It was Roosevelt, however, who made the famous remark that one ought to "speak softly and carry a big stick." True to these realist convictions, in America’s national interest Roosevelt managed to acquire the Panama Canal Zone from Colombia in 1903, allowing U.S. construction of the waterway to begin a year later. His diplomatic skills brought an end to the Russo-Japanese War of 1904–5, for which he received the Nobel Peace Prize in 1906, the first statesman to do so.

In 1919, Wilson also won the peace prize for his efforts to end the recent world conflict. But his foreign policy objectives were based more on idealist concepts—that the United States should not use its power against weaker countries but should exercise concern for the rights of smaller powers. Self-determination was a Wilsonian principle.

The influence of these two extra-ordinary men reaches down to our day. The differing conceptual frameworks they followed in foreign policy continue to define the debate in the 21st century.