While the term had a long history of usage before the 20th Century, duce has become synonymous with dictator Benito Mussolini, who used the title in his capacity as leader of Italian fascism beginning in 1921. After he became the head of the Italian government, his full title became "His Excellency Benito Mussolini, Head of Government, Duce of Fascism and Founder of the Empire." After Mussolini's ouster in 1943, he briefly became head of state of the Italian Social Republic (the so-called Salo Republic) under the official title of Duce until his overthrow and death in 1945.
This position was the model which other fascist leaders adopted during World War II.
- Caudillo, Spanish word for "leader", used by Francisco Franco during his dictatorial rule of Spain in the mid-20th Century. It fell into disuse upon his death in 1975. In the novel In the Presence of Mine Enemies, the title remains in use in Spain well into the 21st Century.
- Führer of the Greater German Reich, a title assumed by Adolf Hitler in his capacity as leader of Germany before World War II. The title fell into disuse upon Hitler's death in 1945. The title remained in use for a longer time in a number of Harry Turtledove alternate history works.
- Poglavnik of Croatia, a title used by Ante Pavelić of Croatia during World War II. The title fell into disuse upon Pavelić's ouster at the end of the war. The title remains in use in In the Presence of Mine Enemies and "Ready for the Fatherland".