The Lord of the Rings War in the North

If you are unable to use war machines on Legendary difficulty, finish the game then find a buddy and have him/her start a new game on easy and join with your high level character. This time however you need to switch classes because the one that was unable to mount the WM still won't be able to use them in this playthrough. I'm not 100% sure about this but the glitch seems to affect the ranger and dwarf classes so just change to the opposite one or the mage and you should be able to mount the WM again. From my experience all the WM kills have to come from one save file (ie playthrough which is misleading) AND from the same class/character -- whenever I changed classes it appeared to reset the counter. So basically any turret kills you had prior to the glitch won't count.

The first chapter has 4 WM and it will only take you 45 minutes to reach them if you hustle -- your high level guy can one-hit kill everything in your path. The first is immediately before the first troll. Have your friend watch your back and aim at the stairs just off to the right, then kill the archers up high on either side. After the troll you will soon come across 3 more WM in succession. For the first 2, just aim down the middle path where the enemies spawn with occasional archers on the sides. The final one is in the circular courtyard after you raise a gate where enemies will pour over the walls on either side in front of you.

I kept track of my kills and was able to get 150 easily off these 4 WM with many enemies to spare. Just make sure your friend(s) isn't killing guys within turret range, and try to hit the regular enemies first if the sappers are present because the game doesn't seem to register kills caused by splash damage when they explode. Best of luck.

I was able to unlock this on my Normal playthrough. I understand the most efficient way to do this is probably to allow War-Machine kills to stack across all of the difficulty playthroughs. However, there seems to be a glitch in New-Game+ that may prevent your character using a WM. If, like me, you do not want to deal with the possibility of a glitch hitting your character, just do what I did.

Get most of the way through your Normal run. The kills you get from WMs while defending the dwarves in Mount Gundabad should get you a good way to your 150. Then, before going on to the last portion(s) of the game (I did it right after finishing Mirkwood) do a little backtracking. Instead of proceeding from your map to the next mission, go back to Fornost and choose Outer Wards. You will come across a WM in this section. Just sprint past all of the enemies and kill the guy manning the WM. You'll probably have to then kill the few enemies who followed you up the stairs. If you don't do this, they'll keep hitting you while you're manning the turret. After your back is clear, fire away in front of you up the stairs. I could usually get around 5 or so kills. Then run ahead and complete the section.

It wouldn't let me choose Outer Wards again, as I was already there. So, I went to Bree, and then turned around and exited to map immediately. Then, Outer Wards again, rinse and repeat, as they say. Each loop only took a minute or two. Not bad for 5 kills a go. Should get you ach. pretty quickly if you're most of the way through the game.

Note: Like I said, this probably isn't the most efficient way, but a good way to avoid the glitch.

Also, just a thought. I didn't get to try this, but maybe the following would be quicker. People say kills might stack across all of your deaths. If this is the case, just kill most of the guys at the defense part in Mt. Gundabad and die. Just don't complete the level until you get all of your kills. I don't know, let me know if that works or not. I know for sure my way mentioned above worked for easy cleanup.

Sorry for the book. Hope this helps.

EDIT: Another Note: I did all of this in Single Player. Maybe it would be a little quicker in Co-Op or Multiplayer.