Reporting from Camp Pendleton and Washington —

On a stretch of clean, white Southern California beach, thousands of young Marines this month charged forward from the sea, leaping from helicopters and landing craft, echoing the exercises conducted decades before when Marines trained for Iwo Jima and Inchon.

It was the largest and most complex amphibious exercise since the Sept. 11, 2001, attacks. It also could be one of the last.

Soon after Marine recruits are given that distinctive, high-and-tight haircut, they are taught about the great amphibious assaults of the past. Those stories, a core part of the Marine identity, “are encoded in our DNA,” said Lt. Col. Bruce Laughlin, operations officer for the exercise, dubbed Dawn Blitz.

But the Marines have not stormed a hostile beach since Inchon during the Korean War. And influential military thinkers — including, most notably, Defense Secretary Robert M. Gates — have begun to question whether the Marines will ever do it again.