The two retired four-stars who have led DOD:

-George Marshall, *after* serving as SecState (“Marshall Plan” etc); and

-J Mattis, during Trump emergency.

Unless a recent 4-star is another Marshall, hard to make case that another ex-general is best pick for DOD..

2/2 Biden + his people (Klain, Sullivan, Blinken etc) are experienced enough to understand why no prez from Eisenhower through Obama put an ex-general in charge of DOD. (Ike of course ex-5-star-general himself—but resolute on civilian control)

If true first strange call by Biden

3/ I agree with the case as argued here, by Jim Golby in NYT, on why a fairly recently retired general (or admiral) is the wrong choice to head DOD.

https://www.nytimes.com/2020/12/07/opinion/biden-defense-secretary-dod.html

4/ On the fetishization of the modern military, from 5+ years ago: https://www.theatlantic.com/magazine/archive/2015/01/the-tragedy-of-the-american-military/383516/