Pearl Harbor demonstrates that war can occur when coercion (e.g., economic sanctions) works too well. To investigate this dynamic, we also engage another important, but controversial, question in this case – namely, whether the United States (US) president Franklin D. Roosevelt (FDR) deliberately sought war with Japan as a way to enter the war in Europe. Contrary to some scholars, our analysis concludes that FDR was aware of the total oil embargo that Acheson implemented and that FDR wanted war. Indeed, the US made only one serious attempt to avoid war – the modus vivendi proposal. FDR supported the proposal because he thought it would give the US more time to prepare. Tojo may have entertained the proposal, but he never received it because Chiang Kai-shek and Churchill vetoed it. The latter needed the US to intervene in the war to increase their chances of winning. This is yet another example of alliances promoting war – in this instance, by vetoing a peace proposal. Finally, we consider why Japan was willing to attack the US, even though it knew the US was more powerful.