The techniques of  the Shorinji Zendo-ryu system go back 2,000 years to China and India when there were only secret fighting techniques reserved for the royal families and elite warriors.  These techniques were so dangerous that only hand-picked and superior loyal individuals were allowed to learn them to protect the Chinese emperor.  Later, some select monks were allowed to learn as well.  The philosophical roots of Zendo-ryu are based on principles of war (martial arts) and spiritual mind training found in India's ancient (4,000 years ago) Sanskrit classic, the Mahabharata.
    The fighting techniques of China were subsequently carried by sailors and ship merchants to the south (Vietnamese kung-fu and Thailand kick-boxing of Muay Thai), as well as the trading partners of offshore islands.  To the north, many of the Northern Shaolin temple techniques branched off into Koryo and Silla, which became North and South Korea.  
    There were many native-born and peasant forms of fighting going back 4,000 years.  All forms of fighting did not originate in the Shaolin temple.  Over many centuries, there was a give and take of ideas and techniques, which added to the refinement of the Shaolin system which eventually found its way to Okinawa.  However, the Shaolin system was the only one that was fused with the mind and body disciplines of yoga breathing and exercise of India.  This is why Bodhidharma developed Chan (Zen) and fused it to the Way of the Chinese current philosophy of Taoism (DO) meaning the spiritual Way.  So, the school (ryu) of Zen and Do were forever united by Bodhidharma with his special mind-spirit development, combined with his unique breathing and physical, natural movements that became the historic martial arts of the Shaolin Ssu(Shorinji).  This method (also ryu) spread to all of the vast areas of China, incorporating many local masters' ideas.
    Okinawa was one of the largest trading destinations for ships and immigrants.  A variety of both highly placed and lower level exponents of this ever-changing and growing Ch'uan-fa Kung-fu started coming slowly to Okinawa about a thousand years later. One of the best known transmitters of this knowledge of historic documents was an 18th century Chinese military official, Kusanku.  His name still is one of our Black Belt katas.  
    My first training with a master was in 1959 with Master Eizo Shimabuku, 10th Dan.  I started with him just after he received his 10th Dan promotion.  He was an exceptional karateka who became the youngest man (before 40 years old) to ever be awarded such a high honor.  He had trained personally under some of the greatest karate masters in Okinawa.  He was the direct descendent of the original Shorinji system transmitted to Okinawa, the founding place of modern karate.  He was promoted by the famous Japanese master, Kanken Toyama, who was the founder of the All Japan Karate Association in 1946.  Toyama was trying to unite all the Japanese and Okinawan systems that had sprung up under different masters under a universal omni kind of karate under one umbrella organization.