He attacked you on the way: the Amalekites attacked the Israelites as they made their way from Egypt to the Promised Land. If a pronoun is used it should agree with the noun in the previous verse; note Good News Translation “They.”

You were faint and weary; or, as in Good News Translation, “tired and exhausted.” The long trek had left the Israelites weak and tired.

Cut off at your rear all who lagged behind you: the Amalekites attacked from the rear and killed the stragglers, who were unable to keep up with the main body of Israelites.

He did not fear God: they were a pagan people, without any concern for God. In many languages it will be helpful to put this clause at the beginning of the verse as follows: “they were not afraid of God, so they attacked…”; or if we keep the clause at the end of the verse, we may say “this showed that the Amalekites were not afraid of [or, did not respect] God.”

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 .