528 MILITARY REFORMpIe .... " All such work units were to be coordinated in a military chain of com-
mand: every five men under a squad leader. with larger units of thirty, a hun-
dred, five hundred, or a thousand. The unit commanders would be held
responsible for the quality of the work; if a wall crumbled within a decade, they
were to indicted for criminal negligence.^69
Yu's concern lest the people be overly burdened with compulsory labor ser-
vice was confined to the limits outlined by classical texts. The dicta against exces-
sive corvee requirements were motivated not only by his desire not to interfere
with agricultural labor during crucial planting and harvesting seasons, but also
to bring the labor of peasants or soldiers under the iron discipline of a military
regime, and although he was willing to countenance the eventual replacement
of private slaves with hired labor, he did not envision a liberal wage market for
the construction of defensive walls.
Yu's lack of faith in the technological skills of Korean construction workers
doubtless explains why he went to such great detail in recording the dimensions
of walls and their slope, the depth of moats, the amount of earth to be moved,
the type of cement, the positioning and height of cannon and archery turrets,
and the daily work per laborer as recorded in certain Chinese sources as Tu Yu's
T'ung-tien, and Ch'i Chi-kuang's Chi-hsiao hsin-shu. Of course, he adjusted the
Chinese figures to Korean conditions, pointing out for example that it took 6,000
monk-soldiers eleven days to repair a wall 2,000 paces long. He calculated the
per capita labor requirement at six men for every two paces of wall length, or
in the case of new construction of strong and long-lasting walls, twelve men
working thirty days to complete two paces of length.
These calculations were his solution to the sorry state of wall construction in
Korea where men were frequently called out for ten-day weeks of work but the
walls crumbled soon after they were built or repaired, The one case of good work
he could think of was the Namhan mountain fort (Namhan sansong, south of
the Han River), but it was a job that took three years to complete, and on the
way half the work had to be redone. "Therefore in fact what should take one
year of construction work actually wastes three years' time, it is said."7^0
Following Ch'j Chi-kuang and Yu Songnyong, Yu's instructions were partic-
ularly detailed on the shape of cannon and archery turrets and ribbed promon-
tories jutting out from the walls'?' He was obviously eager to adopt both the
new cannon and the new kinds of defensive walls that could both resist their
impact and provide secure pods for the lobbing of cannonballs on an attacking
enemy. Yu Songnyong had pointed out in his ten "Essentials of Military Strat-
egy" (Chonsu kiili) that the Korean people were really unskilled in the location
and construction of walls; they just followed the shape of the mountains and
mountain paths. The turrets on the top of the walls were too low to provide cover
for the troops at the top who had to crouch or lie down just to move back and
forth. The spaces allowed for small arms fire were too wide because they allowed
enemy troops scaling the wall to gain easy access. There was also infrequent
use of jutting promontories to provide crossfire or a field of vision to the base