Army Combatives is the hand to hand combat system that the army uses. It runs parallel to many BJJ and MMA gyms. In the beginning, you may be starting on the knees, but as you progress, you may be allowed to fight with open hands like in Pancrase or even fight in the cage.
The interesting part about Army Combatives is that they do a great job of bringing in outside instructors to develop their program and stay as cutting edge as possible.
Here is a great highlight video from the tournaments that took place this year: