The Japanese martial art of Aikido was developed by Morihei Ueshiba and combined his martial arts studies, philosophy, and religious beliefs. Ueshiba's ambition was to create an art that practitioners could use to defend themselves without actually hurting their attackers.
However, do not let this statement mislead you, skilled practitioners can control attackers without hurting them, but they can also cause extreme injury should they so desire.
The philosophy of Aikido is to blend with the motion and force of the attack and redirect the attacker instead of opposing it head-on. This requires very minimal physical strength, as practitioners normally lead the attacker's momentum and redirect it using circuler and turning movements.
Aikido's roots are in the ancient martial art of Dait?-ry? Aiki-j?jutsu, but Ueshiba diverged from it in the late 1920s, due to his philosophical and religious beliefs. While all traditional arts have a common root in believing that violence should be avoided if possible, the majority train practitioners to turn an attackers violence back on them and hurt them.
Ueshiba believed an adept in the arts should be able to control and stop an attack without hurting anyone. While it is a beautiful sentiment, it is often not practical from a self defense standpoint.
Today Aikido is found all over the world in a number of styles, with a wide variation of interpretation and emphasis. However, they all share the fundamental techniques learned from Ueshiba and the majority of them have concern for the well-being of the attacker.