Why does Paul use Roman soldiers to make his points?
Paul uses Roman soldiers because he draws on contemporary things to illustrate spiritual truth. A soldier carried a weapon in his right hand and a shield in his left; Paul applies that picture to the believer, who holds righteousness in both hands.
Les teaches that Paul has a way of using contemporary things to make a point, and a lot of times he uses the Roman soldier. In battle, the Roman soldier carried his weapon in his right hand and his shield in his left—the two items that carried the man into battle. Paul makes that same analogy, but instead of a sword and a shield, the believer has righteousness in both hands. This righteousness is the righteousness of God, which is by the faith of Jesus Christ, unto all and upon all who believe, with no difference between Jew and Gentile.