Where 'Shores of Tripoli' in the Marine Hymn Comes From
In 1801, faced with Barbary Pirates enslaving American seamen and demanding tribute be paid to them, The United States fought the first Barbary War. The second Barbary War was fought in 1815 and The Marines, who celebrate their founding today, fought both those wars.
They got the nickname 'leathernecks' not so much for their own tough hides but for the high leather collars of their battle jackets. These were designed to protect them from cutlass slashing during the battle that would rage as they boarded a hostile ship.
The Marines brought safety and freedom to the seas. Their mission remains the same today.