The Kofun period is named after the tomb mounds that were built for members of the ruling class during this time. The practice of building sepulchral mounds and burying treasures with the dead was transmitted to Japan from the Asian continent about the third century A.D. In the late fourth and fifth centuries, mounds of monumental proportions were built in great numbers, symbolizing the increasingly unified power of the government. In the late fifth century, power fell to the Yamato clan, which won control over much of Honshū island and the northern half of Kyūshū and eventually established Japan’s imperial line.
Burial chambers and sarcophagi in the early tombs were simple and unadorned. Painted decorations began to appear by the sixth century. The bodies of the dead were interred in large wooden coffins; burial goods–bronze mirrors, tools, weapons, personal ornaments, horse trappings, and clay vessels–accompanied the coffins into the tomb chambers. Burial mounds were circled with stones. Packed in rows at the base, scattered on the crest of the knoll, or placed on the sloping sides of the mound were haniwa (clay cylinders). These hollow clay tubes served as stands for offering vessels when the tombs were the focus of community ritual. Although most haniwa are unadorned, some are topped with sculptures.
A notable contribution to pottery during the Kofun period was Sueki (or Sue) ware, first produced in the mid-fifth century. Sueki pottery is usually made of blue-gray clay and is often thin-bodied and hard, having been fired at temperatures of roughly 1,100 to 1,200° C, a range similar to that used to produce modern stoneware and porcelain. Although the roots of Sueki reach back to ancient China, its direct precursor is the grayware of the Three Kingdoms period in Korea. Technically more advanced than Jõmon and Yayoi pottery, Sueki marks a turning point in the history of Japanese ceramics. The potter’s wheel was used for the first time, and Sueki were fired in a Korean-style anagama kiln, made of a single tunnel-like chamber half buried in the ground along the slope of a hill. Green glaze, evolving from the appearance of natural ash glaze that resulted from accidental effects inside the kiln, was intentionally applied to ceremonial objects beginning in the second half of the seventh century.