Thanks mate, this is an older game written in Delphi Pascal lol, I should re-write it in Unity....
If you hold your mouse pointer near the map edge, it will scroll.
Tactics wise: Deal with all the start undead near your villages first, then its only dealing with the waves coming in, by order of the closest to villages.
Beef up garrisons in villages near the edge and leave the centre largely unprotected.