The LORD your God: see verse 10.

Who goes before you: or “who leads you,” or “who is in charge of you” (since in a military campaign the officer in charge led his troops).

Will himself fight for you: this is quite emphatic, and the translation should be equally emphatic. Other ways to express this clause are “He will fight on your side” (Contemporary English Version) or “He will help you as you fight.”

As he did for you in Egypt before your eyes: few if any of the Israelites with Moses in Kadesh Barnea had been present in Egypt when the exodus took place, since all the adults who had left Egypt had died in the wilderness (Num 26.63-65). But the Israelites Moses was addressing had heard the story and knew what Yahweh had done for his people.

Before your eyes means “as you saw [him do it]” (see Good News Translation), and this final sentence may be expressed as “just as he did when we saw him do all those things to the Egyptians” (Contemporary English Version).

Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on Deuteronomy. (UBS Helps for Translators). New York: UBS, 2000. For this and other handbooks for translators see here .