"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.
Semper Fidelis was adopted about 1883 as the motto of the Corps. Before that, there had been three mottoes, all traditional rather than official. The first, antedating the War of 1812, was "Fortitudine" ("With Fortitude"). The second, "By Sea and by Land," was obviously a translation of the Royal Marine's "Per Mare, Per Terram." Until 1848, the third motto was "To the Shores of Tripoli," in commemoration of O'Bannon's capture of Derna in 1805. In 1848, after the return to Washington of the Marine battalion that took part in the capture of Mexico City, this motto was revised to: "From the Halls of the Montezumas to the Shores of Tripoli" – a line now familiar to all Americans. This revision of the Corps motto in Mexico has encouraged speculation that the first stanza of "The Marines' Hymn" was composed by members of the Marine battalion who stormed Chapultepec Castle.
It may be added that the Marine Corps shares its motto with England's Devonshire Regiment, the 11th Foot, one of the senior infantry regiments of the British Army, whose sobriquet is "the Bloody Eleventh" and whose motto is also Semper Fidelis.