An excerpt from an article by Stan Pranin.

I have always felt that the origin of "Iwama Aikido" presents a conundrum for students of the history of modern aikido. For those unfamiliar with the subject, Iwama is a small town in Ibaragi Prefecture where Morihei Ueshiba relocated during the war. It remained the Founder's official residence until his passing in 1969.

What is commonly referred to as Iwama Aikido is a vast technical system consisting of taijutsu, aiki ken and aiki jo techniques. The taijutsu component alone includes somewhere in the vicinity of 600 techniques. Add the various weapons suburi and paired exercises and you have well over 1,000 distinct forms. This curriculum is far more elaborate than those of the Yoshinkan, Aikikai, or that of Koichi Tohei prior to his departure from the Aikikai. It is these latter systems that provide the basis for the styles of aikido that spread in Japan and overseas after World War II, rather than that of the Founder. This is not to imply that the Iwama system is superior but simply that it differs in important ways in content and scope compared to the other major aikido styles.