Zazen reached Japan through a specific, documented transmission: Dogen travelled to Song dynasty China in 1223, trained under the Caodong Chan master Rujing, received dharma transmission in that lineage, and returned to Japan to found Soto Zen, presenting shikantaza as the practice he had received. Japanese Zen historiography traditionally frames this and other transmission lineages as direct, mind-to-mind succession running back to the historical Buddha, a religious claim scholars such as John McRae have shown was itself partly constructed retrospectively by later generations to legitimate specific lineages, a caution that applies to sectarian Zen lineage narratives generally rather than to Dogen's transmission uniquely.
Zen practice remained largely monastic in Japan for centuries before reaching the West substantially in the twentieth century, through figures including D. T. Suzuki, whose writing introduced Zen concepts to English-language audiences from the early 1900s, and Shunryu Suzuki, who founded the San Francisco Zen Center in 1962 and taught zazen to a largely lay, non-Japanese, non-monastic population. That transplantation changed zazen's setting considerably, from a lifelong monastic training embedded in ritual and hierarchy to a practice often taken up by lay students seeking a meditation technique, sometimes without the doctrinal and institutional framework Dogen assumed. Contemporary Soto Zen includes both traditional Japanese monastic training and this looser, internationally dispersed lay practice, and teachers within the tradition differ on how much of the original framework a genuine zazen practice requires.