The other thing probably to mention is that the military is constantly coming up with plans for reorganization. A lot of these plans are really about attempts to take some part of the military's budget from one branch to give to another. The Army and Navy do this constantly. Probably about 1% of any of these plans ever come to any kind of fruition. The army constantly is saying the Marines are redundant and should be phased out or switched over to the Army, along with their budget. This probably happens every single year during intraservice budget planning. There is probably some plan to do away with the marines by the army, or the naval airforce (world's 2nd largest airforce after the USAF) by the USAF, or something similar every year. These plans are rarely taken seriously or get farther than an op ed in some trade journal or a working paper that's circulated.

Just googling "Should the USMC be merged into the US Army" gets 3.5 million hits. It's a discussion topic that gets endlessly debated but never goes anywhere.