special troops type in Long Compaign

[IronHat]

When would it be appropriate to purchase non-regular troops for a battle with your support points?

I'm currently in a Britich LC during the North African campaign and my core consist of the regular Leg coy with tanks. For variety I sometime buy unit from the Indian and ANZAC OOB with support point.

I am thinking of buying some Royal Marine Commandos for beach landing or American Paratroops in the Netherlands, but I don't know when would it be appropriate to buy troops type like the British Army Commandos, the British Paratroopers, or the Gurkha.

More specifically, if I have to assault broken terrain with a lot of roughs or even impassible slop should my leg coy be expecting specialist supporter.