That probably depends a lot on the severity of the condition. Though it's of course much more a problem when actually fighting instead of directing other people fighting. A major question would be how much his men would accept a military leader who can not fight himself. Though given that he was king, there probably wasn't much they could do about it.

--

As I understand it, the modern system of officers and enlisted men is a carry over from when soldiers were devided into nobles and commoners. Which is why we have noncommisioned officers, since nobles wouldn't go directly in tough with the rabble. And if I remember correctly, pretty much all modern militaries are modeled after the European model as a result of 19th and 20th century colonialism. Now nobility is almost nonexistent and rank based on education and training, but the structures are essentually the same.

But are there other models how to organize the hierarchy of an army? I am imagining a highly egalitarian movement that identifies itself strongly by rejecting the notion of elites. Nonfraternization with the troops seems very much out of place there. However, even in civilian organizations, it's generally considered good practice to hire top level leadership from outside rather than promoting staff by seniority, since it just doesn't seem to work so well if you make someone the boss of his long time coworker and friends. Though in a social environment based primarily on kinship groups and clans, leadership because of seniority might be perfectly normal in everyones eyes.

Any useful information you might be able to share?