Tactics for the Swamp (Fortress).

With this setup: 19+ Lizardmen-Gnoll-Gnoll-Snake-Snake-Gnoll-Gnoll, a quick ambush of a Wyvern can be achieved with any low-tier unit (in 18 out of 20 ambushes, it seems to fail due to morale in 2 cases, and always in the same ambush spot with the same result – loss of single units or a complete defeat). Gnolls can be replaced with other single units (Imps, Gremlins).
P.S. Maybe this has been mentioned before, but I didn't see it.