The historical mission of being immediately ready for war, expeditionary missions, and supporting the Navy by taking or holding advanced bases for the Navy filled a niche created by the lack of a standing Army of any size capable of doing those missions.
Before World War II the Army was a cadre designed to expand and incorporate state militias--later the National Guard which was supposed to make the militias more professional. So the Marines were by default the only ready force for war in the short term. And certainly the only force for action abroad.
America now has a sizable and ready Army. So the Marines have to deal with that change in reality. If the Marines are just a second army, they worry they will be seen as redundant.
But with forward deployed forces at sea the Marines still have the edge in reaction time. Especially since forward-deployed Army combat brigades are scarce now and restricted to known hot spots--South Korea and Europe. Despite airlift, the Army doesn't have the flexibility that afloat Marines provide.
Precision weapons and persistent surveillance makes large-scale amphibious operations too difficult until those enemy capabilities are suppressed. But the missions of being immediately ready for war, expeditionary missions, and supporting the Navy remain good objectives.
Being ready for war includes both unit readiness and the ability to quickly get to a fight by being forward deployed and able to deploy quickly from American soil.
Expeditionary includes small-scale amphibious operations against opposition but should mostly mean deploying in larger numbers to secure ports and being able to fight immediately with the close cooperation of the Navy until the Army can reinforce the Marines if needed.
Supporting the Navy is more important now. It can include seizing ports to deny them to the enemy or make them available to our Navy--which means the Marines should master urban warfare. It can include taking enemy island or coastal bases to end their anti-ship and anti-aircraft threats. It can include dispersed operations with anti-ship and anti-aircraft weapons deployed on temporary or permanent advanced bases to enable the Navy to operate more effectively close to capable enemies.
The Marines can act as a second Army when needed. And as I've noted, the Marines are actually the most significant "allied" ground force sent to fight at the Army's side abroad since the end of World War II.
As the author concludes about the Marines:
Hopefully they will continue to be America’s force-in-readiness that can respond quickly to an array of potential threats as they have always done. This is what the United States still needs whether the American people and Congress realize it now or not.
I'm an Army guy. But I would never want to lose the Marine Corps.
