Although historians debate at what point it is suitable to refer to Shinto as a distinct religion, kami veneration has been traced back to Japan's Yayoi period (300 BCE to 300 CE). Buddhism entered Japan at the end of the Kofun period (300 to 538 CE) and spread rapidly. Religious syncretisation made kami worship and Buddhism functionally inseparable, a process called "shinbutsu-shūgō". The kami came to be viewed as part of Buddhist cosmology and were increasingly depicted anthropomorphically. The earliest written tradition regarding kami worship was recorded in the 8th-century "Kojiki" and "Nihon Shoki". In ensuing centuries, "shinbutsu-shūgō" was adopted by Japan's Imperial household. During the Meiji era (1868 to 1912 CE), Japan's nationalist leadership expelled Buddhist influence from kami worship and formed State Shinto, which many historians regard as the origin of Shinto as a distinct religion. Shrines came under growing government influence and citizens were encouraged to worship the Emperor as a kami. With the formation of the Japanese Empire in the early 20th century, Shinto was exported to other areas of East Asia. Following Japan's defeat in World War II, Shinto was formally separated from the state.