Summary: 
               
            Par 1) (Beg of Parsha,Deut 21:10): "If you go out to war and the L-rd, your G-d, will deliver etc."  going out of doubt and through this - "and you take his captives" 
             
            Par 2) The reason that we make a blessing on a Maaka (guard-rail) (even though we do not make a blessing on a  Mitzvah that is due to danger) because   "so that you shall not cause blood [to be spilled] in your house"  is a secondary aspect     
             
            Par 5) The war against Amalek in Avodah 
               
            Par 9) The aspect of Chai Elul       
             
              |