The labor force was made up of three groups: soldiers, common people,
and criminals.
Soldiers
made up the main construction group. This was the case with the
building of the wall of Northern Qi (550-557). Also, during the
Qin Dynasty (221BC - 206BC), 300,000 soldiers were redirected to
build the wall after General Meng Tian conquered the Huns. Still,
it took nine years to finish the work. In order to take care of
the soldiers and make them feel settled, the court even arranged
for widows to marry them.
Millions of common people were called up to build the wall. Northern
Qi's wall, starting from Xiakou to Hengzhou, used 1,800,000 laborers.
A section of Sui's (581 - 618) wall in Inner Mongolia required more
than 1,000,000 men to build. Besides the first 300,000 soldiers,
Qin's wall required another 500,000 common people to complete the
work.
Criminals were forced into labor as punishment. During the day,
they were ordered to take turns patrolling the wall, while at night,
building and extending the wall. They were required to serve four
years of hard labor according to laws at that time.