The origins of aikido lie in Daitō-ryū Jujutsu (later called Daitō-ryū Aiki-jujutsu) which was handed down within the Aizu clan from long ago and revived by Sōkaku Takeda (1859-1943). He learned kenjutsu (sword) from a young age and also received a licence in sōjutsu (spear). Aikido was founded by Morihei Ueshiba (1883-1969) who was one of Takeda’s students. Ueshiba also practised judo, kenjutsu (sword), sōjutsu (spear), jukenjutsu (bayonet), etc. The techniques of Daitō-ryū Jujutsu absorbed the principles of the sword and spear and had a great technical influence on later aikido.
Kenji Tomiki (1900-1979) started receiving instruction in aikido (Daitō-ryū Jujutsu at that time) from Ueshiba in 1926. When the dan rank system was introduced in 1940 he received the first 8th dan which was the highest rank. He is known as the founder of competitive aikido.
Ueshiba was a very pious man and spread aikido from a religious perspective particularly in the latter part of his life in contrast to Tomiki who sensed the necessity to modernize aikido. He knew that judo and aikido have a common origin and saw that the principles of aikido techniques are no different to those in judo. The techniques that Kano omitted from competitive judo are incorporated into aikido and grouped as atemi waza (striking techniques) and kansetsu waza (joint techniques) with the participants separated.
Aikido is viewed as a composite martial art because its principles embrace those of both kendo and judo. This synthesis is not straightforward but broadly speaking the chances to apply atemi waza are consistent with the timing opportunities to stab or cut in kendo whereas kansetsu waza use judo principles to set up a technique so that it is easy to apply. It is also worth noting that the combative range of competitive aikido lies between that of judo and kendo. Also, one player holds a weapon and the other is empty handed rather than both armed or unarmed.