The oath of office all commissioned officers in the US military take:
“I, (state your name), having been appointed a (rank) in the United States (branch of service), do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foriegn and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the office upon which I am about to enter. So help me God.”
Lieutenant General James R. Clapper considered it an advisory.
Perjury.