Our military is apolitical and only follow orders from the top down. They would only defend the Constitution when they are ordered to and instructed how to do it.
It may surprise you to know that in the enlisted ranks (non-officers) we swore to obey the orders of officers appointed above us.
What to Know About Obeying an Unlawful Military Order
Notice the oath states, “I will obey the orders of the President of the United States...”, but the Uniform Code of Military Justice (UCMJ) Article 90 states that military personnel need to obey the "lawful orders of his/her superior.
*snip*
The UCMJ actually protects the soldier in this situation as he/she has a moral and legal obligation to the Constitution and not to obey unlawful orders and the people who issue them.
p.s. Nuremberg.
Enlisted service members also take the oath at the beginning of each term of enlistment. Officers take the oath only once at commissioning.
WWG1WGA
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)