Karibash has not only the numbers to preform a quicker takeover, but as well as maintaining a high CS even with casualties. If he gets half of his men killed or wounded, then he still have perhaps 800-900 CS left, which is nothing to scoff at. Basically I guess its like the concept of the Persian Immortals, one falls and another immediately takes his place (for awhile).
Of course, it does come with the natural drawback of what I would imagine a hideously slow travel time, compounded by Karibash old age. Oh and if battle is not given then I wouldn't want to know the repair cost and time for that kind of unit.