And I may be wrong here but Kirby can’t “resign” from the Navy. He can retire at a future date, i. E. Put in his retirement papers.
He has been reassigned to a different job, I’m pretty sure, so he will still be in uniform until he retires.
He serves, as all uniform personnel do, at the “pleasure of the President” and has to have his retirement request approved by the chain of command...
I think I got that right.
Officers can resign their commission pretty much anytime after an initial obligation (6 years for Service Academy graduates, 3 year for OTC, Reserves. In some cases they may be asked to stay on but it’s rare to have it forced.