The Assyrians used a variety of methods to obtain the workforce that built their cities. One of the primary ways was through forced labor, which involved capturing people from other lands and making them work on construction projects. The Assyrians also used prisoners of war and slaves as laborers. Additionally, they may have used conscripted laborers from within their own empire, which would have included peasants and other lower-class individuals who were required to perform labor in service to the state. Overall, the Assyrians relied heavily on forced labor to build their cities and monuments, which was a common practice in many ancient civilizations.