Being bum rushed by enemies from all ends? got plenty of wealth with no place to go? then don't despair! the good fellows at Outpost Operations (TM) are able to recruit Mercenary Units for you.
Unlike normal units, mercenaries are not trained piecemeal, but are instead raised as picked bodies of troops ranged by tribe, and so can bring a wealth of experience and power to the board in a quick instant. Yet, however, make no mistake: raising mercenaries is not an easy thing, for they cost exclusively of wealth. And a lot of it, too. Nevertheless, their presence at your Outpost grants those with the wealth to raise massive armies or expand their actual forces with no problems.