Amphibious warfare has become the defining competency of the U.S. Marine Corps. Although Marines pride themselves on being able to do anything on short notice, it is being able to force their way ashore from sea bases that makes them genuinely unique. With most of the world’s population and commerce located within 200 miles of the sea, that’s a valuable capability to have. But there is one key item missing from Marine plans for the future: a successor to the 40-year-old Amphibious Assault Vehicle. That vehicle was state-of-the-art when it debuted during the Vietnam War, but today it is deficient in armor, reliability and even buoyancy. So cancellation of a replacement in 2011 after 15 years of development was a serious blow to the Corps. That’s why Marine leaders are pushing ahead with plans for an “Amphibious Combat Vehicle” despite difficult fiscal and political conditions. I have written a commentary for Forbes here.