Here are some topic questions to help you get started on your paper.
Pick any country involved in World War II (ex. Great Britain,France, USSR, United States, Germany, Italy, Japan...) What were foreign relations like for that country before the war? How did their diplomatic relationships evolve during the war? What were their foreign policies like after the war? How did the war impact their alliances? How did it impact their relationship with their enemies? What relationships did they develop with neutrals? Which countries joined the United Nations after the war? What does this tell us about diplomatic relationships during the war?
What type of diplomacy did resistance groups like the Free danes use? How were they able to gain Allied assistance? Did the Allies reach out to help them?
Did Great Britain and the United States have a close relationship? What methods did Great Britain use to try to persuade the US to enter the war? How does propaganda play a role in the US involvement in the war? Would the U.S. have entered if Japan hadn't bombed Pearl Harbor?
Look at the United States-Japanese relationship today. How has it changed since World War II? Did the U.S. and Japan have a good diplomatic relationship before the war? How did the relationship change after the war? Did the status of victor-loser create tension between the two countries? How has the U.S.-Japanese relationship evolved since the war?
The war resulted in the division of Germany in East and West. How did the Soviet and Western European/U.S. relationship change? Were there any diplomatic tensions between the Soviets and the other Allied countries during the war? How did the diplomacy from the war affect the later Anti-Communism movements?