How to play Knalgans
From The Battle for Wesnoth Wiki
General Knalgan strategies:
On the first turn when you have a random opponent it is good to get a mixture of units that will be good attacks. They can sustain a lot of damage before they die, so the first wave of an opponents attack is likely not to kill any of your units. This will allow you to pick off particular units you wish to get rid of before your opponents next turn. Focus on killing their high damage units first, if possible, if not, kill and weaken as many units as possible to decrease the chances of success for your opponent on his second turn of the attack.