Sage Santangelo is a second lieutenant in the United States Marine Corps.

I awoke to Eminem blasting hours before dawn at Quantico Marine Base. A fog of breath and sweat permeated the cold January air as I joined 104 other nervous lieutenants hauling gear to the classroom where we would receive our first instructions. With body armor, Kevlar, a rifle and a huge pack on my 5’3’’ frame, I must have looked like a child next to the buff guys assembling for Day 1 of the Marine Corps’ Infantry Officer Course.

I was one of four women in the group, bringing the number to 14 female officers who had attempted the course since it was opened to women in the fall of 2012. All the women so far had failed — all but one of them on the first day.

I wasn’t thinking about that, though. I was excited to have a shot at the Marines’ premier training course.

I’m typical of a Marine in that I’ve always sought out challenges. I flew my first solo flight when I was 15 and got my private pilot’s license three years ago at 21. I’ve climbed 10 of the 14,000-foot peaks in my home state of Colorado. As an ice hockey goalie for more than a decade, I put myself in the path of pucks flying at 80 mph.

I expected that this, though, would be the toughest experience I’d ever had.

There’s a lot of mystery surrounding the arduous 13-week course used to screen and train potential infantry officers. Past participants are asked not to talk about it, in order to preserve the uncertainty for future classes. So we lieutenants had little idea of what we were getting into. But we knew that the first day is always the Combat Endurance Test, and that it pushes people to the limits of their physical and mental capabilities.

Several hours into the test, I jogged past a lieutenant who was overcome with cramps and vomiting on the side of the road. The temperature hovered just above freezing. A blister bled on my foot and sweat poured down my face, yet I felt relatively good. I had completed all the tasks so far within the time allotted, and I was determined to make it to the end without showing any weakness. A packet of MRE cheese spread gave me new life. I shook frost from my uniform, threw my pack on my back, slung my rifle and jogged on through the woods.

But there came a point when I could not persuade my body to perform. It wasn’t a matter of will but of pure physical strength. My mind wanted more, but my muscles quivered in failure after multiple attempts. I began to shiver as I got cold. I was told I could not continue.

That night I forced every step to be normal as I dragged myself — weighed down by gear, disappointment and exhaustion — back to the barracks. It was no consolation that 28 other lieutenants, including the other three women, failed along with me or that the Infantry Officer Course commonly drops 20 to 25 percent of each class. As I sat in my room, famished and waiting for pizza that seemed like it would never arrive, I reflected: Why did I fail?

The question matters because Marine leaders have been watching female participants like me to help them decide how to integrate women into units and positions whose primary mission is to engage in direct ground combat. The Marines have until Jan. 1, 2016 , to request any exemptions from the Pentagon directive to open all combat roles to women. “If members of our military can meet the qualifications for a job — and let me be clear, I’m not talking about reducing the qualifications for the job . . . then they should have the right to serve,” then-Defense Secretary Leon Panetta said when he rescinded the direct-combat exclusion rule last year.

Marine Sgt. Maj. Micheal P. Barrett, the senior enlisted adviser to the commandant, affirmed: “Our plan is deliberate, measured and responsible. We will not lower our standards.”

1 of 18 Full Screen Autoplay Close Skip Ad × Myths of 2014 View Photos Fact or fiction? A collection from Outlook’s popular Five Myths series. Caption Fact or fiction? A collection from Outlook’s popular Five Myths series. MYTH: Sanctions never work. “The most complete academic studies on the matter show that sanctions lead to concessions from the targeted government in one out of every three or four cases,” writes Daniel W. Drezner in “ Five myths about sanctions . “That is a far cry from never working.” Here, President Obama and German Chancellor Angela Merkel leave a joint news conference at the White House in May. The leaders discussed additional sanctions to punish Russia for its incursion into Ukraine. Charles Dharapak/AP Buy Photo Wait 1 second to continue.

My failed attempt at Quantico, and the fact that no woman has yet made it through the Infantry Officer Course, shouldn’t be interpreted as evidence that women can’t handle combat environments. To date, 13 female Marines have passed the two-month enlisted infantry training course at Camp Geiger in North Carolina. While that course is significantly less demanding than the one at Quantico, it is still grueling — participants must lug 85-pound packs on 12-mile treks through the woods — and it establishes the standard for enlisted warfighters.

Even more telling, on the front lines, where roles have already blurred, women have performed exceptionally well in traditionally male situations. Consider Sgt. Leigh Ann Hester . A Kentucky National Guard soldier, Hester was leading a team on a mission outside Baghdad in March 2005 when her convoy was attacked by insurgents. She orchestrated a counterattack with grenades and M203 rounds. The unit killed 27 insurgents, including three taken out by Hester with a rifle, and not a single soldier was lost. Hester became the first woman to receive a Silver Star since World War II.

So what’s held women back in the Marines Corps Infantry Officer Course? I absolutely agree that we shouldn’t reduce qualifications. For Marine infantry officers, mistakes mean risking the lives of the troops you are charged to protect. But I believe that I could pass, and that other women could pass, if the standards for men and women were equal from the beginning of their time with the Marines, if endurance and strength training started earlier than the current practice for people interested in going into the infantry, and if women were allowed a second try, as men are.

Female lieutenants aren’t as prepared as male lieutenants for the Infantry Officer Course’s tests of strength and endurance because they’ve been encouraged to train to lesser standards. Officer Candidates School, where all Marine officers start out, is segregated by sex. I was in an all-female platoon. We worked with the men on a few occasions but never competed with them. That was odd for me. As someone who grew up playing hockey on boys’ teams, I was used to facing off with the guys.

The Basic School, where I reported after graduating from Bowdoin College in 2012, has long been co-ed. But physical double standards persist. In the Physical Fitness Test, for example, a male perfect score is achieved by an 18-minute three-mile run, 20 pull-ups and 100 sit-ups in two minutes. A female perfect score is a 21-minute three-mile run, a 70-second flexed-arm hang and 100 sit-ups in two minutes. There was a move to shift from arm hangs to pull-ups for women last year. Yet 55 percent of female recruits were unable to meet the minimum of three, and the plan was put on hold.

I understand not wanting to discourage new recruits. But dual standards highlight and foster differences in a way that undercuts the goal of integrated military units. Women aren’t encouraged to establish the same mental toughness as men — rather, they’re told that they can’t compete. Men, meanwhile, are encouraged to perceive women as weak. I noticed that women were rarely chosen by their peers for some of the harder tasks in basic training.

Yes, men have biological advantages in tests of upper-body strength. But women can do pull-ups if given enough time to build that strength. (I did 16 in my last physical fitness test, and I have no illusions that I’m the most qualified female Marine.) Recognizing biologically based advantages and disadvantages and developing training programs that work to balance them are key.

It would be especially helpful if the Marines allowed people to decide on an infantry career earlier and offered some infantry-oriented training earlier, too. Basic training doesn’t include enough physical gruntwork under a combat load. More exercises such as running, jumping and climbing while wearing a flak jacket, Kevlar and a pack would help build strength and endurance. They would also help prevent injuries by increasing bone density. My class had only a month between the end of the Basic School and the start of the Infantry Officer Course. I wish there’d been more time to train to the endurance test’s demands.

I also would have liked to have had the opportunity to try the course again. The Marine leadership has said it doesn’t want female lieutenants taking the course multiple times, at least until combat positions are available to women, because it doesn’t want to delay the rest of their training. Yet many of the men who failed alongside me in January are back at Quantico, training to retake the course in April.

They’re more likely to pass the second time around. The course is designed to create young officers who thrive in an uncertain environment. Going into the endurance test, you don’t know how far you’ll have to go, what the obstacles will be or what time constraints will be imposed. The uncertainty makes the test overall much more difficult than any of its individual parts. Some of the details change for each new class. But the male lieutenants who have taken it before have an advantage in that they know generally what to expect.

For me, the next stop is Marine flight school in Pensacola, Fla. I’ve been told, though, that it will be 12 months before there will be an open slot. So reporting for Infantry Officer Training next month wouldn’t have hurt my career.

UPDATE, April 4: In response to this essay, Gen. James F. Amos announced that female Marines would be allowed to retake the Infantry Officer Course, as male Marines are, and he offered Sage Santangelo a posting in Afghanistan while she waits for a flight school opening.

I’ve always been taught that failure provides the greatest learning opportunities. My failed effort at Quantico has helped me better understand the needs of the Marines on the ground and will allow me to better support them in the future. At the same time, I love the Marine Corps philosophy that failure should never be viewed as permanent or representative; it is an opportunity to remediate. Marines cannot meet standards all the time. What do we do? We train until every Marine is competent. “No Marine joins the Corps to be a failure,” Gen. James F. Amos has said. “We don’t raise them up that way.”

It’s frustrating to me that there are still doubts about whether women are capable of handling combat environments. The women who have been awarded for their valor in combat, and the women who have died in combat for their country, have already answered the question about capability.

Now, instead of passively evaluating their performance, we need to figure out how to set women up to excel in infantry roles. My hope is that the Marine Corps will allow every Marine the opportunity to compete. And that when we fail, our failure is seen simply as a challenge to others to succeed.