10 November 1775 in Philadelphia, two battalions of “Continental Marines” were formed to fight on land and sea. Which means that the USMC predates the founding of the United States by about half a year.
Other than an ill advised dissolution from 1783-89, they have been defending America from it’s enemies ever since.
As the power and prestige of the United States grew, so did the mission of the USMC. That included developing counter insurgency strategies and tactics during the time between World War 1 and World War 2. Much of that information is still used to this day.
Other nations have patterned their marine forces on that of the USMC.
A consistent record of protecting America through good time and bad is something or which to be proud.