How to use JD Ultimate in Gears 5 is a little tricky for first time players. JD's Artillery Strike is a very powerful ability, but using it isn't forwardly explained. Here's how you can use JD's Ultimate, Artillery Strike, in Horde Mode.
How to use JD Ultimate in Gears 5: Artillery Strike
To use JD's Artillery Strike, first you must ensure your enemy is out in the open. The ability is unusable if your target is indoors or if there is an obstruction overhead. However, if you accidentally go to use it in this case, you won't go into cooldown and you'll be free to try again.
Next, you'll have to mark your enemy. This is where a lot of players get confused. To mark an enemy, get them in your crosshairs and press the left stick in. Then, you'll be able to launch your Artillery Strike with no problems.
Artillery Strike will drop five artillery rounds for massive damage. It is most useful against Bosses or a big crowd of enemies.