"Service members have a legal, enforceable duty to obey only lawful orders from those authorized to give orders (violating them is prosecutable by court-martial under Articles 90 and 92 of the Uniform Code of Military Justice), and a legal excuse (and moral grounds) for disobedience under the limited circumstances of receiving an unlawful order. The issue of presidential immunity for the commander in chief—whether absolute or presumed—is absolutely irrelevant to the underlying lawfulness of the order itself."
https://www.lawfaremedia.org/article/can-the-military-disobey-orders-in-the-seal-team-6-hypothetical
I hope someone points out that
1. Treaties between countries are law within the countries that sign them,
2. the NATO treaty requires members to resolve disputes diplomatically
3. therefore any order to carry out military action against another NATO country is an illegal order and must be refused, REGARDLESS of what the president says, even if it comes directly from him.
One would hope so, but dear leader has done so much wrong and hasn't seen a jail cell...