I've been training in martial arts since the 1980s and consistently since the '90s. I am a 2nd-degree black belt in Kenpo Karate.
Tai Chi is an ancient art of combat from China that makes use of fluid movement for parrying and redirecting attacks with a riding force, using the opponent's force against him. It includes the use of strikes, kicks, locks, and throws. It is a soft style martial art, as opposed to hard styles which use hard blocks, kicks, and strikes. It is a beautiful art form which uses a set of moves put into a dance that is used the world over as a means of physical and mental fitness. However, Tai Chi definitely has combat applications.
Other arts use similar techniques and principles that are very much like that of Tai Chi. Let's explore these arts and what they encompass.
Wu Shu is a conglomeration of various Chinese Kung Fu styles put together to attempt a uniformity of systems for the purpose of competition. It has strong elements of Tai Chi but features very fluid and aesthetically beautiful movements and acrobatics. The Tai Chi sword is a common feature during competitions and is elegant and deadly, like much of the systems of Chinese boxing. It shows balance and grace, but also power and speed.
Tai Chi Sword at Wushu Competition
Jeet Kune Do
Many people don't realize that Bruce Lee's father was a practitioner of Tai Chi and instilled its movement and principles in his young son early on in his life. Bruce was a practitioner of Gung Fu, of course, and studied Wing Chun. He incorporated many Chinese systems into Jeet Kune Do. The fluid circular movement of Tai Chi certainly influenced the formulations of Jeet Kune Do.
Bruce absorbed what was useful and that was one of his trademark statements. Your movement might need to be circular and fluid, it depends on circumstance. So, naturally, Jeet Kune Do ends up including Tai Chi style movement, among all the other more direct and aggressive movement it needs depending on circumstances. All in all, a good fighter does show grace because he is efficient; efficiency and fluidity go hand in hand.
Aikido uses the opponent's force against him and relies on fluid circular movements. This form of defense requires a riding force, not a hard bucking force, so the actions are definitely going to resemble Tai Chi.
Foot maneuvers and arm and hand movement circle around the opponent and upset his base, taking him off his feet and placing him in a comprising position or slamming him into hard objects. The idea is not to go force against force, negative into negative, but to go with the attacker and put him down and out.
Kenpo has both linear and circular movements and emphasizes continuity of motion, which means movement must flow and not end until the fight is finished. In this way, it bewilders the opponent and is rapid and overwhelming. So, the actions of Kenpo are very similar to Tai Chi. It also has elements derived from Tai Chi's cousin arts from China, like Choy Li Fut and the southeast Asian arts that are heavily influenced by Chinese boxing, like silat and others. Because so many arts are interrelated, you end up seeing a striking similarity between Tai Chi and arts like Kenpo.
All of these arts mentioned have elements similar to Tai Chi: Heavy emphasis on circular fluid movement, use of locks and throws, use of strikes and kicks, and what is generally termed a soft style. While they differ in approach, some more aggressive, some more yielding, the principle of redirection and bewilderment remains intact. The idea is to move deceptively and continuously to upset the balance of the opponent and to catch him off guard. This can only really be done with circular movement that rides his force and brings him down. This is the common ground that these arts have with Tai Chi.