Marine Corps Postmortem
Dave Pinion
On February 8th 2040, Congress passed a law that abolished and dissolved the United States Marine Corps and merged its personnel and assets into the Army, Navy and Air Force. It should not have come as a surprise to anyone. After a bruising two-month war with China in which the U.S. never landed a meaningful punch, there was bound to be a reckoning across the entire Department of Defense.
In the decades building up to the conflict, China did not attempt to mask its military modernization nor its ambitions to displace the U.S. as the dominate power in Asia. China spent decades studying the U.S. method of fighting and openly developed systems that exploited U.S. vulnerabilities. The U.S. way of warfare had reached an evolutionary dead end and was easily picked apart by 21st century technology.
https://smallwarsjournal.com/jrnl/art/marine-corps-postmortem