Posted on August 23, 2020Two Steps From Hell (Uncommon Valor) “Semper Fidelis” (“Always Faithful”) is the motto of the Corps. That Marines have lived up to this motto is proved by the fact that there has never been a mutiny, or even the thought of one, among U.S. Marines. CONCLUSION Semper Fidelis was adopted about 1883 as the motto of the Corps.