Key point: The Marines are shifting investment from expensive legacy platforms to large numbers of cheap, small, expendable systems enabling naval forces to operate effectively inside a contested zone even if they absorb substantial losses.
Many defense experts believe that defense spending has peaked and may decline in future years. This will intensify the longstanding competition for finite resources among the U.S. military services. In that climate, it will be more important than ever for the U.S. Marine Corps to understand and explain its unique contributions to national security.
As long as there is a requirement to fight on land, at sea, and in the air, the answer for the Army, Navy, and Air Force, respectively, is fairly straightforward. The case of the Marine Corps is more complicated because of the hybrid nature of the service: it is a naval force with its own air assets, capable of fighting on land.
The Marines have answered the question regarding its function in different ways as geopolitical circumstances have changed. During World War II, the Fleet Marine Force operated closely with the Navy, specializing in the conduct of amphibious assaults against defended beaches in order to seize advanced naval bases.
During the Cold War, the Marine Corps reinvented itself as an expeditionary force in readiness, able to respond quickly to emergencies around the globe, but it also served as a second land army in Vietnam – a role it reprised in Afghanistan and Iraq. Marine Corps flexibility has drawn both praise and a periodic identity crisis—with some periodically calling into question whether the U.S. needs a Marine Corps.