The engineer is a specialized troop type. It fights at only half the strength of rifle infantry. Its important to realize that engineers are not combat-engineers. Engineers are your construction troops! They can perform a wide variety of tasks, that only they can perform. They can build roads and bridges, the can demolish bridges and locations and they can construct a variety of locations including ports, airfields, fortifications and factories/shipyards. They can also upgrade resource locations.
The answer to the question if you need engineers depends strongly on the scenario you are playing. Lets discuss the four most prominent reasons to get engineers…
First of all if resources are scarce in your game world then you must try to upgrade your oil wells and mines as soon as possible. For upgrading resource locations you need some raw materials, but also you need an engineer unit on the actual hex to provide the EP (engineer points) necessary to make the upgrade.
Secondly if the map contains several continents or islands and requires you to make amphibious invasions into enemy territory in order to win the game you should definitely build some engineer units to go with the first or second wave of your invasion. This because in all likelihood you will not be able to capture a port town immediately and thus land at a weaker defended stretch of coast. When doing so you will run into supply problems since supply does not easily flow from sea to land without the help of a port. Use an engineers to quickly build a port on a just conquered coastal hex. (like for example the Mulberries during Normandy landings)
Thirdly if the map you are playing is lacking roads you should build engineers to construct them. Without an adequate road network your empire will have serious supply, transfer and production deliveries. Although it is possible to play and organize your empire in a sort of decentralized fashion it is not recommended.
Fourthly if the map does not contain that many towns and you want to keep your troops under air cover then you should get some engineers to build yourself some airfields. Keep in mind that level I fighters provide an air umbrella maximum 5 hexes away, check the amount of hexes between towns on the map to see if you’ll troops will run out of air cover or not.
A good size for an engineer unit used for road building is 20-30 engineers. 20-30 engineers generate 40-60 EP a turn. Enough to build 2-3 road hexes a turn or after 1 turn of waiting to upgrade a level I resource hex. A good size for a engineer unit used in repairing bridges and building fortifications is 40-50 engineers. For using engineers to help amphibious invasion I would use at least 60 engineers to make sure you have the required 100 EP as quick as possible. I would recommend issuing trucks to your engineer units to give the some radius to move them quickly to a spot of need.
