A recent proposal in Congress to change the name of the "Department of the Navy" to the "Department of the Navy and Marine Corps" brings to light something that most people do not realize. The United States Marine Corps (USMC) is not part of the Navy, but a fourth service that is closely intertwined with the Navy and one of two military organizations that make up the Department of the Navy. Before World War II, there was no Department of Defense. There was the War Department, led by the Secretary for War, which controlled the army and a lot of planning functions for future war making. Then there was the Navy Department, led by the Secretary of the Navy, that controlled the navy. Since 1798, the Marine Corps had been a separate organization within the Navy Department. But because the Marine Corps was a much smaller organization than the navy, it did not assert much independence. Things changed during World War I, when the marines used their reputation as a "can do" organization, and reputation for hard fighting, to get permission to expand and form a brigade size unit for fighting in France. Following up on that, the first marine division was formed in 1942, and during World War II the Marine Corps grew to include six divisions and nearly half a million troops. It was no longer a corps, it was an army. After World War II, the Marine Corps was larger, in proportion to the Navy, than it had ever been before. The marines fought attempts to reduce them to a tiny size after the war, and struggled through the 1950s to get a seat on the new (since 1947), Joint Chiefs of Staff.
Using adroit public relations skills, the marines got Congress to pass several laws that protected them from downsizing, or elimination. But the marines continued to be the junior partner in the Department of the Navy. When that department got its budget each year, the marines had to fight hard for every dollar it got. And it was still navy ships that carried the marines to distant war zones, and thousands of sailors (including the medical personnel in the rifle battalions) that provided logistical and other support for the marines. But in the downsizing of the 1990s, the army got cut 30 percent, the marines only 15 percent.
The proposal to change the name of the Department of the Navy is mainly cosmetic, and not something the navy would find worth waging a battle with Congress over. Which is how the marines like it. One small victory at a time, and it adds up over time. The U.S. Marine Corps is the largest and most powerful marine organization on the planet. The marines intend to keep it that way. It won't be easy. The army and air force are united in getting the marines to take their share of cuts, and the navy is inclined to let the marines fight their own battles.