Construction Units - What do they do?

[Dinglir]

I do get that they deploy and build rails.

But apart from that, do they do anything else?

For instance, do they help frontline units in fortifying?

I could probably read the manual, but I am not sure I trust it on this particular topic.

[Telemecus]

Yes they do help in fortification. For example directly assigning them to units certainly does increase fortification rate in tests (Axis side).

By the manual they should also help if construction is in their direct HQ, or in the next higher HQ if the chain through all the lower HQs is 5 hexes or less. So this is the one case where SUs do help in higher commands. I am quite certain this is true from experience on the Axis side at least.