Blitzkrieg and an awesome begining to domain play

My players have just ended a campaing of conquest on an orc realm, first the invested 80000gp in hiring mercenaries from bigest cities in the area (wich gave them less than 30000gp worth of troops as they have to pay the first bach of mercenaries while waiting for the second and so on)

then they march to a nearby orc domain of 40000 families and procede to storm caslte after castle using the dwarven machinist flyning armor to scout ahead and hitting the orcs before they could gather in strength and focusing on killing the enemy generals with magic and trickery to disband the larger armies. 

Now after 5 sessions of battles they stand as the lords of the same 40000 goblin and orc families, and have the intentions of reforming the goblin society and convert them to the veneration of Sol Invictus. 

Its interesting that they did that being level 7, and now they can spect to reach level 9 at least just by maintening their domain.

Mages are entusiastic about doing some magic research, speacialy designing new spells. 

Notes to myself as to why the orcs go defeated:

-an army without a good proportion of archers is really vulnerable vs a large group of archers.

-Killing commanders can really turn the tides of a battle.

-Always keep the general safe.