This is a collection of fight clips from high-level international judo competitions, highlighting the ground-fighting portion of judo.

Although judo is well known for its standup grappling (nagewaza) and especially its throws, it also has a large ground grappling component (newaza), which consists of a number of dominant positions and pins, joint locks, and chokes. Judo's newaza roots lie heavily in Fusen-ryu jujutsu, which impressed Kano after Kano's school was completely dominated in challenge matches between the two schools. Judo newaza was taught to and developed by the Gracies, which resulted in Brazilian jiu-jitsu and submission wrestling, and thus has historically been one of the biggest influences in submission grappling. Judoka will often tease Brazilian jiu-jiteiros by calling BJJ "Basically Just Judo", although there is much debate about that point.

In competitions, a fighter may forcefully throw an opponent on his back for ippon, or a winning point. However, if a throw fails and the fighters end up on the ground, the fight is allowed to continue for a certain time, where a fighter may attempt to stand up, stall until the referee resets the fighters in standing, pin his opponent, or submit the opponent with a joint lock or choke.

A pin must be held for 25 seconds to result in ippon. Chokes may be held until an opponent taps out or passes out, either of which will result in ippon. Joint locks may be held until an opponent taps out, the joint is disabled, or the referee ensures the lock is secured and ippon is awarded. This last rule was implemented because many high-level judoka would allow their arms to be broken rather than submit, hoping for the chance to continue fighting even with a broken limb.

One of the heaviest criticisms of modern competition judo is the weakness of many judoka's newaza technique, especially in light of what BJJ, submission wrestling, and sambo have brought to the competition table in cross-style tournaments and MMA matches. Judo competition rules generally heavily favor ippon by throw, since committees decided that matches with people being whipped around in the air would look much more interesting than people rolling around on the ground, so rules tend to de-emphasize the use of newaza:
1. Competion rules ban the use of leg locks, spinal locks, and several other submission holds due to their inherent ability to cause more damage than other submissions, like chokes.
2. Since judoka are only given a limited amount of time to fight on the ground, often fighters will immediately turtle up and stall for a stand-up. On top of that, a judoka who wants to fight newaza must show the referee that he is "attempting a technique", so he must often spaz out in order to show that he's fighting for some sort of position or hold. This results in a very unified approach to newaza, i.e. fast bursts of speed and strength to attempt a few attacks, while other flavors of newaza (slow and crushing passes, paced transitions, and locked-down submissions) rarely, if ever, occur in competition.
3. Since the mere act of the judoka standing up will cause the match to be paused and the other fighter to be stood up, there is no development of defenses or attacks against standing opponents or moments when an opponent could stand, i.e. attacking from and passing the guard, open guard, leg attacks, and submissions that can be finished even if an opponent stands. Triangles, for instance, can be finished even if an opponent squats and tries to stand up, before an opponent can get a chance to slam his attacker.
4. Backmount is not considered a pin because it doesn't put a judoka's back on the mat, although it is one of the most dominant positions in a real fight. Judoka will very often give up their back in order to turtle and stall until the stand-up, although such a tactic is useless and very dangerous in a non-judo fight.
5. Judoka typically spend much more time practicing tachiwaza than newaza, so they never get the practice time to develop technique on the ground. Also, instructors often don't give appropriate instruction for newaza, so newcomers without newaza experience will often miss out on key principles like "position before submission".
6. Rules against cross-facing and neck cranks make some chokes harder to catch. On top of that, some referees will incorrectly call fouls for neck cranks when the contact being made is merely to lock in a choke. (The rear naked choke and the triangle choke come to mind.)

Although I believe that judo competition rules must be changed to force judoka to learn good ground technique in accordance with Kano's original intentions, judo newaza still has a lot to offer the world, and even as it stands, it is nothing to be trifled with, as this video shows. Running clock chokes, flying flip armbars, hell-strangles, judo's got them all. On top of that, judo newaza will always remind other submission grappling arts of what they need to remember: standup and groundfighting can't be separated. A good throw leads into dominant ground positions and submissions, and a well-rounded fighter is dangerous on two levels, not just one.

Judo uber alles.