"let themselves be defeated before the people of Ai." The phrase "before them" represents what the people of Ai would see and think. The phrase "be defeated" can be stated in active form. Alternate translation: "let the people of Ai think that the Israelites were defeated" or "let the people of Ai think that they had defeated the Israelites" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-activepassive]])