I really liked "Small Unit Leadership" as having some good lessons for business leaders as well.

One thing that stuck with me is how the military can't just fire the people that don't work out, so there's significant time spent on how to get underperforming people / units back into shape.

https://www.amazon.com/Small-Unit-Leadership-Commonsense-App...

I would also strongly recommend "Small Unit Leadership: A Commonsense Approach": https://www.amazon.com/Small-Unit-Leadership-Commonsense-App...