Stealth mode

Stealth mode is a mode available to certain units in Age of Empires 3. In this mode a unit becomes invisible to the enemy but can still be seen by the user. While in this mode, units are considerably slower than normal. When the technology Spies is researched a player can see other player's stealth units. Spies [not the technology the unit] are able to see other stealth units as well as being able to go into stealth mode themselves.