Can someone explain to me the requirements to build a depot. Because the manual's list of requirements is plainly not comprehensive. Sometimes I am able to build a depot and sometimes not. I have no idea why.
Manual lists just this:
Depot: It can be built at a cost of two Supply Wagons or by two
transports ships if a harbor or anchorage is in the region.
The tooltip will tell you that you may not be able to build a depot because of a lack of control or required units, but it does not tell you how much or how many.
Such an important mechanic, but again a lack of information.