The Kofun era and early state formationAn example of a medium- sized keyhole- shaped tumulus is Kurohime- yama, in Sakai City,
Osaka. It is 144 meters long, built in the second quarter of the fifth century. An excavation of a
pit- style burial chamber in the frontal mound resulted in the discovery of twenty- four sets of
iron armor. All twenty- four sets consisted of iron helmets and iron cuirasses, and twelve of them
were accompanied by gorgets and shoulder protectors. To date, twenty- four remains the largest
number of armors discovered in a single tomb. It is important to note that the twenty- four sets
were discovered in the frontal mound, while mounded tombs were dedicated to the occupant of
the rear mound. In other words, the iron armor was deposited in a subordinate burial chamber.
An even larger quantity of iron armor would likely have been deposited in the main burial
chamber, the circular rear mound, which had been destroyed before the archaeological excava-
tion of 1946. This also leads to a further speculation that far larger quantity of iron armor would
have been deposited in the giant tumuli more than 200 meters in length.
Another archaeological discovery that gives clues to understanding fifth- century military
organization resulted from the Nonaka square tumulus, 28 meters per side, located near the 224-
meter Furuichi- Hakayama keyhole- shaped tomb, in Fujiidera City, Osaka. Excavation of the
Nonaka tomb resulted in the discovery of one set of iron armor in a wooden coffin (probably
worn by the individual buried therein), 373 iron arrowheads in a presumably wooden box placed
next to the coffin, and ten additional sets of iron armor in another presumably wooden box
placed next to the box containing the arrowheads.
This quantity is greater than in the case of the more or less contemporary 159-meter- long
Mozu- Ōtsukayama tomb. In the course of deconstructing this keyhole- shaped tomb in Sakai
City, archaeologists discovered eight clay coffins. In coffin No. 1, an iron cuirass was discovered,
and in coffin No. 2, five cuirasses, tassets, and greaves were discovered. This comparison strongly
suggests that whoever was buried in the Nonaka tumulus was in a position very important to
military affairs.
The position of the Nonaka square tumulus is evidence for one more aspect of the political
structure in the fifth century, the emergence of a bureaucracy. The giant keyhole- shaped tumuli
of the fifth century are distinguished by accompanying small circular or square mounded tombs,
which are referred to as baichō or “satellite tombs.” The practice of building satellite tombs existed
only in the fifth century. Archaeologists tend to assume that, while those buried in the 150-meter-
class keyhole- shaped tumuli and the circular and square mounded tombs were middle- and
lower- level elites somewhat independent from the highest- ranking chief, those buried in satellite
tombs were direct vassals of the highest- ranking chiefs. Some archaeologists further speculate
that those buried in these satellite tombs were bureaucrats serving the chief, each carrying out
different functions.^26
This relationship between the paramount chief and his bureaucrats was replicated in a few
local polities, such as Kibi (150 km west of the Kinai, in presen- day Okayama prefecture). This
indicates that even in the Middle Kofun period, some local polities were still autonomous and
could replicate the political structure of the center. This would be evidence for indirect control
of local regions by intermediate- class elites.
In the Middle Kofun era, considerable evidence for socially stratified trade networks and, to
some extent, a tribute system appeared. Based on discoveries of large quantities of iron armor,
archaeologists suspect that, although we have not yet unearthed a workshop for armor produc-
tion, the production of iron armor was monopolized by the central polity. The production of the
jade and talc beads, essential for rituals in the Kofun era, also came to be under centralized control
in the fifth century. While the production of jade objects took place in the Hokuriku region (the
Sea of Japan coastal region of central Honshu) where jade was quarried in the Early Kofun era,
the production of jade and talc beads took place in Nara during the Middle Kofun era. Although