Here is a brief chronology of Japan's imperial line. By tradition, Akihito is the 125th in an unbroken succession, but historians dismiss the first 14 as mythical figures and say the line was broken in the sixth century. The dates of the 15th to 28th emperors are in doubt.

Circa 660 B.C. - According to court historians in the seventh and eighth century, Jimmu, a direct descendant of the Sun Goddess Amaterasu, ascends the throne as Japan's first Tenno, or emperor. This is now dismissed as a myth.Early fifth century - First historical emperor, Ojin, is a strong chieftain from the Yamato region, now Nara prefecture in central Japan. He was a descendant of the horse-riding tribes said to have come to Japan from Korea in the late fourth century and conquered it.

531 A.D. - Emperor Kimmei starts his reign. He was the first emperor whose reign dates are backed by documentary evidence. His function was mostly that of high priest in the indigenous shamanistic religion now known as Shinto.

593 - Suiko, the first female ruler, accedes to the throne. Although closely associated with Shinto, the imperial family becomes protectors of Buddhism.

661 - Tenchi, the first emperor to have political as well as religious sway over his subjects, starts his reign.

806 - Kammu, the last emperor to rule as overlord, dies. Hereafter, power passes to the Fujiwara family who rule as regents. Capital moved from Nara to Kyoto in ninth century.

1185 - Seven-year-old Emperor Antoku perishes with the Heike military clan. Power passes to the Genji clan, the head of which became the first shogun who ruled from Kamakura, near Tokyo.

1274-1281 - The shogun successfully defends Japan from Mongolian invasions.

1333 - Emperor Go-Daigo briefly usurps power and overthrows the Kamakura shogunate, but his wars with the military clan result in the split of the imperial line and two rival emperors.

1868 - The last shogun hands power back to Emperor Meiji, who proclaims an empire and starts modernizing Japan. Emperor given sovereign status, becomes commander-in-chief of the armed forces and is revered as a "living god."

1912 - Meiji dies, Taisho succeeds him.

1926 - Taisho dies, Emperor Hirohito, known posthumously as Showa, succeeds him. Japan begins period of military expansion into Asia, which culminates in World War II.

1945 - Hirohito agrees to unconditional surrender. Emperor becomes "symbol of the unity of the people" and is relegated to ceremonial duties. Hirohito disclaims divine status.

1989 - Hirohito dies at age 87. Akihito, his first son, succeeds to the throne and inaugurates a new era of Heisei (achieving peace).

1990 - Akihito undergoes formal enthronement ritual.