Slaves

Summary
Slaves are a special economic brigade used to staff resource buildings, similarly to workers.

Rather than being recruited from cities, slaves are created by capturing surrendered enemy brigades or by capturing resource buildings with enemy workers already in-them, who will then be turned into slaves. If the Slave Trading skill is unlocked in the skill tree, additional slaves may be purchased in cities that have a Slave Market upgrade constructed.

"Slaves are non-combatants that can be moved into resource buildings such as farms, mines or logging camps to generate resources. Slaves are created when capturing resource buildings with workers in them or by capturing combat units that have surrendered. Slaves do not consume food, cost gold, or contribute to the garrison. Slave units can be merged together into groups of up to 20 men."

- In-game Description

History
Slavery has existed since the dawn of civilization, already being a very well-established institution in the oldest written records. Though a select few cultures, such as the Persians, formally banned slavery, most of the civilizations of the ancient world extensively practiced it, and slaves formed a major part of the economy of the Greeks and Romans.

There was a wide variety of slavery in the ancient Mediterranean. People could become slaves due to being prisoners of war, as a punishment for crime, due to being in debt, or simply because they were born as children of other slaves. The treatment of slaves varied widely across cultures, being brutally treated in some whereas other cultures had laws in place to protect them from cruel treatment by other citizens. In some of the most lenient cultures, such as Athens, certain categories of slaves may have been very well-educated and even allowed to own property and operate their own businesses in exchange for a tax-payment to their masters, though other less fortunate slaves were still forced to work hard physical labour in poor conditions.

Tactics
Compared to workers, slaves have the benefit of not requiring any upkeep in gold, which is important given the very large workforce needed to fully operate all the resource-producing buildings a player will have as the game progresses. Even though individual worker brigades aren't very expensive, the upkeep cost for all these workers will quickly add up over time. Subsituting normal workers with slaves can greatly boost a player's economy. The player should always be aiming to capture as many slaves as possible from defeated enemies and use them to replace earlier worker brigades, which can then be disbanded to save costs.

Ressource nodes can be staffed with 20 (40 with upgrade) workers or slaves, hence slave brigades should always be of a size that makes optimal use of worker spaces in the resource node. Slave brigades can be split using the corresponding icon in the command panel. They can be merged by selecting a brigade with the left mouse button and then clicking on a second brigade using the right mouse button.

When slaves are disbanded in one of your cities, a small percentage of them will join your cities recruits. Thus this is a viable way to increas recruits if you already have all resource buildings staffed.