Brief history of SGI

History of Buddhism
Buddhism originates from the message of Shakyamuni, also known as Gautama or Siddhartha, who lived in the Indian subcontinent around 2,500 years ago. Born as a prince, Shakyamuni left his life of luxury on a spiritual quest to understand the four sufferings of life: birth, sickness, aging and death. Eventually he awoke to the true nature of life and became known as the Buddha or "awakened one."
His teachings were later compiled into sutras, and numerous schools of Buddhism sprang up as the teachings spread from India after his death. The Buddhist tradition embraced by SGI members is based on Mahayana Buddhism, the tradition which spread northwards through China and Korea to Japan.
Nichiren, a 13th-century Japanese priest, researched all available Buddhist texts and asserted that the Lotus Sutra encapsulates the heart of Buddhist teachings. This sutra reveals that a universal principle known as the "Buddha nature" is inherent in all life. Nichiren established the practice of chanting Nam-myoho-renge-kyo to bring forth this potential, which enables each individual to overcome life's inevitable challenges and develop a life of wisdom, courage and compassion.

Soka Gakkai International
The Soka Gakkai (literally, "Society for the Creation of Value") was founded in 1930 by educator and author Tsunesaburo Makiguchi as a group of reformist educators. Makiguchi drew inspiration from Nichiren Buddhism to develop the organization into a broader-based movement focused on the propagation of Buddhism as a means to enable people to tap their inner potential and ultimately reform Japanese society. Facing oppression from the Japanese militarist government, Makiguchi and his closest follower Josei Toda were arrested and imprisoned in 1943 as "thought criminals"; Makiguchi died in prison in 1944.
After his release, Toda promoted an active, socially engaged form of Buddhism as a means of self-empowerment--a way to overcome obstacles in life and tap inner hope, confidence, courage and wisdom. He used the term "Human Revolution" to express the central idea of Nichiren Buddhism, that all people are capable of attaining enlightenment in this lifetime.
Toda was succeeded as president in 1960 by Daisaku Ikeda, who further developed the Soka Gakkai as a movement of empowered, socially engaged Buddhists. Soka Gakkai International (SGI) was founded on January 26, 1975, as a worldwide network of Buddhists dedicated to a common vision of a better world through the empowerment of the individual and the promotion of peace, culture and education. Under Ikeda's leadership, the SGI has developed into one of the largest Buddhist movements in the world, fostering and promoting grassroots activities in areas such as nuclear abolition, human rights and education for sustainable living. It currently consists of 90 independent affiliated SGI organizations and has 12 million members in 192 countries and territories worldwide.

Source http://www.sgi.org/resource-center/introductory-materials/brief-history-of-sgi.html