I would consider a thesis that looks like this:
William Golding's novel Lord of the Flies explores the themes of power, purpose, vengence, instinct, and corruption in order to connect to the history of WWII.
In each of your body paragraphs, draw connections from Lord of the Flies to what occured in WWII. For example, in WWII, we had the ultimate quest for power. Some leaders reacted to the situation as did Ralph in order to do their best for the people. Ralph tried to plan shelters, food, and the signal fire, although his leadership was not strong and he could not get the people to act until situations were extreme. Ralph could be compared to the officials of the US and Britian during WWII. On the other hand, Jack sought a power that demanded all follow his rules only and his rules were extremely inhumane. He could be compared to the dictatorial power of Germany's Hitler.
Read up on the historical connection and the themes that enotes provides as linked below.