Although Engineers possess decent armour, they are normally unarmed, relying on commanders to clear the battlefield for them, or more likely, to be transported in APCs.
Red Alert universe
Both the Allies and Soviets succeeded them with the second generation of engineers.
Engineers have two purposes:
1. To capture enemy structures. Depending on the health of the building, it can take up to five Engineers to break into a fully armoured enemy structure. A workaround is to damage the building until it hits red condition and then capture the building.
2. To repair own buildings. The engineer can bring a building instantly to full health. The unit disappears in the process, however.