Final answer:
The expansion of Islamic trade networks was one of the most important enterprises of Islam, besides creating the civil service system.
Step-by-step explanation:
One of the most important enterprises of Islam, besides creating the civil service system, was the expansion of Islamic trade networks. Islamic traders ventured into various parts of the world and used trade routes like the trans-Saharan trade routes to facilitate commercial exchange. These trade networks not only facilitated economic growth but also contributed to the spread of Islamic culture and ideas.