An article by James Dunnigan from StrategyPage.com:
The U.S. Marine Corps is again fighting, not for its existence but for the current number of marines on active duty. It works like this. The U.S. Army, facing growing budget cuts, is talking about reducing its active duty strength to 420,000 by the end of the decade. The marines don’t want to go below 174,000. Since the U.S. Navy also has its own ground force (NECC) of 40,000 sailors the Navy Department (containing the navy and marines) has 214,000 ground troops and that would mean the navy and marines would have a third of U.S. ground forces. This strikes many in the army, and Congress, as odd and the marines are fighting hard to persuade Congress to ignore the odd and keep 174,000 marines on active duty.
Read more at: http://www.strategypage.com/dls/articles/Why-American-Marines-Are-Turning-Into-Soldiers-11-25-2013.asp
Dunnigan, J. (2013) Why American Marines Are Turning Into Soldiers. Available from World Wide Web: http://www.strategypage.com/dls/articles/Why-American-Marines-Are-Turning-Into-Soldiers-11-25-2013.asp. [Accessed: 29 January, 2014].