In this mission you will be facing two Pig opponents that start with 4000 gold each. Since your starting gold is 8000, the battle can end quickly.
Buy weapons from the market and build an army of 25 macemen, 25 crossbowmen and 25 horse archers.
Use the horse archers to attract and avoid the first Pig's crossbowmen's fire while you place your crossbowmen close to his castle backed by your macemen (if he tries to attack them with his macemen). If he already has set up a square tower don't waste your troops trying to kill all the crossbowmen on top of it and just go for the kill.
Repeat the strategy for the second pig since you shouldn't have lost that many troops if you move your archers well enough.
While moving your army towards the first Pig, start producing leather armor and crossbows back home. This is in case you don't manage to kill the second Pig with the remaining troops. If that happens, sell crossbows in to buy maces and quickly move your 10-15 macemen against the second enemy lord.
Apart from the above mentioned weapon production, there is no real need to build a strong economy and make the battle last longer.