From The Washington Post:

In short: We are chilled to our bones at the thought of a coup succeeding next time.

The potential for a total breakdown of the chain of command along partisan lines — from the top of the chain to squad level — is significant should another insurrection occur. The idea of rogue units organizing among themselves to support the “rightful” commander in chief cannot be dismissed.

All service members take an oath to protect the U.S. Constitution. But in a contested election, with loyalties split, some might follow orders from the rightful commander in chief, while others might follow the Trumpian loser. Arms might not be secured depending on who was overseeing them. Under such a scenario, it is not outlandish to say a military breakdown could lead to civil war.