I'm not sure the Danes were ever military only, Denmark was also an agricultural society during the viking period. As I understand it, the viking raids were in fact organised around the agricultural calendar, with the two raiding seasons taking place after the harvest and after the sowing. And of course the Vikings were interested in acquiring farming land and often settled and farmed in their places of conquest.
A more apt comparison might be pastoralist raiders as mentioned in Turchin's War and Peace and War, whose nomadic lifestyle led naturally to the development of military skills that could be applied in raids on settled communities. Turchin wrote a lot about the Tatars and the Mongols could also be a good example.
I didn't mean for the imperfect example of the Danes to take it off tangent, it was only to illustrate a people I could think of for whom raiding was integral but your examples or any other is just as well. I think someone (civ) could have taken it further and been sociopathic and only relied on military force for survival. Obviously there are benefits in diversifying, but I think while not ideal, it's possible and could work, in some circumstances.
Until they established city centers, trade routes, spread religious freedom to among their subjects, developed population centers and their agricultural output, standardized exchange rates and quality bars, created systems of news and material delivery, and all that other stuff.
Their empire was, of course, extremely short, as it collapsed with the death of their Great Kahn soon after it established itself and its following leaders abandoned the previous inroads in the West to focus on the prize of capturing China (that ultimately failed).
Our history tends to focus on the expansion of their empire rather than its subsequent administration, I think in part for that reason.
I suppose so, I forgot western civ was one battle loss away from not existing as a continuous entity. So yeah, military only seems to be possible, even if the Mongols were not 100% faithful to this strategy, I think someone could have been successful.
A more apt comparison might be pastoralist raiders as mentioned in Turchin's War and Peace and War, whose nomadic lifestyle led naturally to the development of military skills that could be applied in raids on settled communities. Turchin wrote a lot about the Tatars and the Mongols could also be a good example.