Medium Troops

Medium troops are level 4 warriors, and probably make up the bulk of your standing army. They are professional soldiers, who have served their time as light troops and then undertaken extra training. They expect only to be used in times of war or civil insurrection, and don’t do basic patrols or civic policing. They are a 1bp upgrade from Light Troops.

Settlement Watchtowers and Walls come with Town Guards - their troops can't be upgraded.
Wilderness Watchtowers, Base Camps, large camps and Redoubts all come with Scouts - their troops can't be upgraded.
Forts come with a Unity of Town Guards and another of either Scouts or Light Cavalry - their troops can't be upgraded.
Military Jetties do not start with any troops, but may house up to six marine troops added as further developments - their troops can't be upgraded.
Residential Properties and Mercenary Bases come with Private Guards - their troops can be upgraded.
All other buildings can start with any type of light troops - their troops can be upgraded.

All medium troops are built with the Medium Troops Template, and are a 1bp upgrade from Light Troops.
Cavalry Troops must have the Cavalry Troops Template applied as well.