A engineer soldier is not a original soldier unit from the game, The Conquerors. They aren't used often until a person has researched a wall.
A engineer is always used for making walls. Without a engineer a wall cannot be made, even if researched. They are mostly used in either the beginning or middle of a game due to having a defense, if there is no truce available. To make a wall, put a engineer between two wall columns that are within range of each other (or else it will not work) and it should automatically make a wall.
Attacking Strategies Edit
Due to engineers having no attack or healing ability, they are mostly only used for walls. Keep them near walls at all times if you want to repair a wall quickly.
- Apparently you have to research engineers this is safe to assume to be a glitch.