234 SOCIAL REFORMSince he believed that the hereditary aspect of Korean slavery was a depar-
ture from Chinese norms, he was naturally interested in its origin in Korea. Con-
trary to conventional wisdom he made no mention of Kija's law, and he was
unable to find any instance of hereditary slavery in Korean history in the Three
Kingdoms period (ca. the first century B.C. to A.D. 668). Slavery existed, to be
sure, but enslavement occurred only as punishment for prisoners of war, crim-
inal action, embezzlement, or robbery. He thus dated the origin of hereditary
slavery at the beginning of the Koryo dynasty when T'aejo (Wang Kon) enslaved
many of the opponents of his regime and gave them to his merit subjects for
their private slaves.
Yu presented no positive evidence for his interpretation, but he probably
deduced its origin in early Koryo because of the I039 matrilineal inheritance
law and the clear existence of hereditary slavery by the mid-Koryo period. By
so doing he stripped hereditary slavery of any legitimacy conferred by a puta-
tive origin in remote antiquity, whether in China or in ancient Choson under
Kija's sage rule. Yu also remarked that the laws of the Koryo state forced peo-
ple into slavery, causing an increase in the slave population to 80 or 90 percent
of the population. a view that was popular in the early Choson period.^107 This
situation was exacerbated by the violation of (italics mine) the matrilineal rule
of succession (chongmobop or chongmojibl5p) that was supposed to limit the
inheritance of slave status in the case of mixed commoner-slave marriages to
the children of slave mothers. Since in practice the offspring became slaves if
either of the two parents were a slave, "All this means is that people are forced
into slavery, and once a slave, there is no way out of i1."108
He appears to have assumed that the law had remained on the books since
I039, albeit neglected in practice. Thus, he could not have known that the matri-
lineal rule itself had been severely criticized for contributing to the increase of
the slave population. Yu explained that "the fault is not with the matrilineal suc-
cession law [in mixed marriages]; the error [is to befoundl in the slave law [itself];
that is, the law by which slavery is [determined by] heredity [nobi isejibOp]."
Another factor was the onerous burden of military service, which commoners
sought to avoid. Because slave status conferred exemption from military ser-
vice (at least prior to 1 593), many commoners often arranged marriages for their
children with private slaves. 109
Yu cited Yulgok's criticism of slavery as well as a lengthy memorial of Cho
Hon to King Sonjo on his return from a mission to China in 1574 in which Cho
made an invidious comparison of Korean defensive capabilities relative to China
and attributed the cause of Korean weakness to slavery. I 10 The reason, Cho said,
why Chinese border areas were secure despite the need to defend numerous scat-
tered towns and cities was because, contrary to contemporary Korea where slaves
were exempted from military duty, the whole popUlation, except for the scholar-
officials and those engaged in farming and commerce, could be recruited as sol-
diers. For that matter, during the Three Kingdoms period in Korea everyone could
be recruited for military service on behalf of the king because slavery had not