The Marine Corps does not expect a flood of women to volunteer for the course, though more than one has for the next round. Women make up only 6 percent of the Marine ranks, and the school’s nature deters many Marines, no matter their gender.

(This reporter graduated from the course in 1988; on the first day, a lieutenant regarded by instructors and peers as one of the most fit students suffered a heart attack and died.)

The current course begins with the Combat Endurance Test, which was added in the 1990s.

Last week’s test began in a classroom after midnight. A captain addressed 96 students, each sitting beside a mock M-16A2 rifle (real rifles are not issued until after the first test) and a backpack loaded with food and equipment.

“Notebooks away,” the captain said. “No notes.”

From this moment on, the captain said, for an amount of time unknown to the students, they would be continuously evaluated. Students who failed would be assigned a noninfantry job.

After a lieutenant completed each leg of the test, the captain said, there would be another instructor who would explain the next task. The test was timed, but the lieutenants would not know how much time was allowed for many events, or over all. This uncertainty was intended to force every student to go as fast as he could, never knowing how much energy and food to conserve.

No one was to help anyone else, the captain said. Speaking was forbidden, except when addressing instructors, with one exception. “If you are injured at any time, it is the only time you will talk to another Marine,” he said. “Legitimately injured,” he added, “As in, ‘I have a bone sticking out of my leg.’ ”