I'm not going to get into which martial art is the best. Everyone has their opinion. However, I trained in Muay Thai (MT) for awhile and I can tell you, for practical techniques in getting your enemy down fast, it's one of the best. If I were CO of insurgent training, I would recommend this as the standard for every insurgent.
Here we have Duke Roufus, one of the best trainers today, giving a demo on the kick. Notice how he explains the technique.
Here's another great view. If you have powerful legs, you'll disable someone right quick. Notice the hip movement.
Here we have two negros during an MMA match. Notice how the one negro, Vernon White, who has a white wife by the way, Gets his ass kicked with some MT techniques. Actually, this is some sloppy fighting but notice the devastating kick at about 5:12. That's classic MT! Then watch the head kick, not the best form but effective. Notice how the elbows, knees and hands are employed. That's why it's called the Art of the 8 weapons: hands, elbows, knees and feet (shins, really).
Here is Duke's website: http://www.groundfighter.com/details/prodid/133.html Check out some of the videos, there are even Kettlebell vids, another great way to build core strength! If you have a buddy, you could split the cost of the video and train together.
Fight smart. Fight to win.