You wouldn't want to call Erik Hildinger's Warriors of the Steppe exactly "scholarship." There are nol footnotes. The bibliography is extensive, but not exhaustive. And the tone is too easy and direct. But he's got a remarkable story to tell, which he presents with crisp conviction.
Executive summary: for something like 2200 years--until the implementation of gunpowder--nomads from Central Asia repeatedly made a nuisance of themselves with their more "civilized" neighbors and more than once, bid fair to put these neighbors permanently out of business. They succeeded in doing so for two reasons: one, they deployed a set of lethal tactics that their neighbors--unaccountably by any measure--persistently refused to learn. And two, they forced these neighbors to accept their (nomadic) definition of war.
Genghis Khan was their prime avatar--with his descendants, perhaps the most successful and effective military presence in history, certainly in the last thousand years (yes, counting Napoleon and Hitler). But there were many others: Scythians, Parthians Huns, Magyars, Bulgars, Avars, Seljuks, Crimean Tatars, even the Jurchids who imposed on the Chinese their last foreign dynasty.
There were failures: not every oppporunistic nomad became Genghis Khan. Sometimes, the invaders failed because the defenders used their own tactics against them (think Mamluks); sometimes because they fell into anarchy and lost their fighting edge (think Dmitri Donskoi). But it is impossible to name any other culture that so persistently and so consistently inflicted pain on its neighbors.
The complex of tactics is as simple as it was devastating. Ride light, durable, fast-moving horses. Take the opponents by surprise. Surround them and devastate them with a hail of arrows. Retreat--or appear to retreat, but wait until your pursuers have broken ranks and then turn and open fire. The surprise is not that it worked once, but that it worked time after time after time. And there was no mystery: the first account is in Herodotus, about 450 BC. One cannot escape the notion that arrogance and indifference and cultural blindness had at least as much to do with the nomads' success as any peculiar virtue in technique.
The matter of "choosing their own war" is perhaps more complicated, but at least as interesting. The key point is that the step nomads, at least traditionally, weren't interested in conquering cities. They were interested mainly in pillage, and cities were merely an incidental detail. So they had no interest in the war of position and domination so central to the strategic thinking of the West. Even Genghis Khan, who used siege engines (he learned about them from the Chinese), and who build a semi-durable network of polities---even Genghis Khan, so they say, was actually in a city only once in his life.
One invigorating lesson from Hildinger's narrative is that all war is stylized, conventional: even "total" war hasw its norms and its conventions, and a fabric of values from which the protagonists cannot easily escape. It's a lesson profitably to be learned by anybody who hazards combat with an enemy whose reading from a wholly different page.