Never Leave a Man Behind is an Achievement in Halo Wars that is obtained when the player finishes a match with 5000 net resources tributed to their temmates on Memorial Basin except in Deathmatch. It is worth 15 Gamerpoints.
Start a 2v2 game on easy as Forge. Build up your bases with at least 4 supply pads each.
Build a small attack force and take as many bases as you can without engaging the opponents.
When you have a total of 7500 resources, simply send everything you have to your ally.
You can choose to quit, win or lose the match but you will gain the achievement whatever the outcome.