In close-quarters combat, it's called "the fatal funnel."

As the point man, you're about to kick in the door and go straight through it. But you'll have to be swift. Get stopped in the doorway and you could find out the hard way how the fatal funnel got its name. Weapon at the ready, body armor in tow and adrenaline saturating your veins, you breach. Just then, blinding chaos ensues. Behind you, a grenade detonates, knocking you off your feet and into the 8×10-foot room, separating you from your three fellow soldiers. Smoke fills the air. You hear your team taking on small-arms fire outside and instinctively spring to your feet and check your M4 rifle. Suddenly, an enemy emerges from the darkness of a corner in the room, his footsteps through the splintered door fragments and broken glass — barely audible over the ringing in your ears — serving as your only warning. Screaming and wielding a knife, he grabs at your weapon. You're now in a fight for your life. What do you do? Though CNN might lead you to believe that wars in the 21st century are won and lost with Predator drones and surgical missile strikes, situations like the one described above are far more common than you might think. And it's here, on the predawn, humid grounds of Georgia's Fort Benning at Army Combatives School, where many of those battles are decided — not only by churning out soldiers who are tactically superior, but also by inspiring and cultivating a warrior ethos that has redefined what it means to be "Army Strong."

0600 INSTRUCTOR PT

The drive into Fort Benning — situated on the Georgia-Alabama border — is dark and peaceful at 0545, Army speak for 5:45 a.m. Banks of tall trees, barely visible against the early morning sky, frame the road leading into the base, which was established in 1918. Soldier barracks and base housing windows stand quiet, shades drawn. By all appearances, Fort Benning still slumbers. But as M&F photographer Ian Spanier and I approach Army Combatives School (ACS), it's clear that someone's awake.

Soldiers walk casually in and out of the old mat-lined hangar that has been home to the program since its inception in 2002. The uniformed students begin warming up inside, partnering up in twos and starting the basic grappling drills that form the backbone of the program taught here. Minutes later, the instructors start heading out to the lawn adjacent to the hangar — carrying ropes, tires, sleds, medicine balls and weight plates — and in an instant, the morning calm is shattered.

It looks more like a strongman summit than traditional morning PT (physical training). Staff Sgt. Damien Stelly, a 6', 205-pound soldier with four deployments to Afghanistan under his belt, attacks a 450-pound tire lying on its side, bending into a deep squat and grabbing it with an underhand grip. In one smooth motion, he uses his legs and back to lift the tire to his waist before quickly and carefully turning his hands and pressing the tire up and over until it crashes back to the earth with a deep, chest-rattling thud. Three flips in each direction and ACS instructor PT is officially open for business.

Off to the side, Staff Sgt. Chris Camphouse is using a 30-pound sledgehammer to whale away violently with a steady cadence at another oversized tire. Master Sgt. Lewis Fletcher, who at 6'4" and 270 pounds looks more like a middle linebacker than a typical soldier, power-cleans a 100-pound medicine ball from the ground, pauses briefly and tosses it over his head, walking forward a step to allow the ball to slam to the dewey earth behind him. Then he picks it up and does it again.

Staff Sgt. Aaron Cooper, meanwhile, is running 25-yard sprints — with a 75-pound sled dragging behind him. This draining circuit, which also includes two other power-building exercises, mercifully terminates after everyone has spent a minute with each primitive implement. After a full minute of rest, the action starts anew.

As the sun breaks the horizon, the base slowly comes to life. Fresh-faced, flag-toting recruits jog past ACS in formation every few minutes, and traffic steadily increases. The instructors of ACS, on the other hand, have already been working for close to an hour. The punishing strength circuit is a daily routine for the instructors at ACS, who know that in a fight, strength will always be a tactical plus.

"Size and strength are advantages in a fight, just like athleticism," says Matt Larsen, director of the Army Combatives program and author of the Army's field manual (read: bible) on modern combatives, a blend of boxing, jiu-jitsu, judo and wrestling. "If somebody has advantages, you have to overcome them in a different way. Some jiu-jitsu guys say that size and strength don't matter. Well, that's baloney. If someone is bigger and stronger, that's an advantage."

Larsen, a retired Ranger who worked combat operations in Panama, Iraq and Afghanistan, is the Army's authoritative voice on fight culture, but he's keenly aware of the role that strength and overall health play in the life of a soldier. As the architect of the functional-strength circuit his instructors plow through every morning, as well as the drills the students will do for the next eight hours, he thinks in terms of combat performance and longevity.

"Our PT here at ACS is the way our bodies are designed to work," he says. "We want to know what's the most powerful way to do something."

While pro bodybuilders such as Jay Cutler and Toney Freeman train for size and aesthetics, Larsen's disciples train to overtake an enemy, subdue a prisoner or carry a wounded comrade out of harm's way. This training is, quite literally, based on life-or-death scenarios. When you'd normally drop a set of dumbbells because lactic acid is screaming through your muscle bellies, these guys push through it. If you can't get it done on this lawn, you won't do it under duress in Fallujah.

0810 DRILLS, DRILLS, DRILLS

It's just after 8 a.m. and it's already terrifyingly warm, even for August. The South is baked in record-setting heat this week, and here we sit, the damp, sticky Southern air slowly drenching Spanier and me, but it doesn't seem to bother the Level III class — there are four levels total, each more intense than the one preceding it — getting started on the mats. These students are in week two of their Level III instructor training. Following four weeks of instruction, each student will return to his or her (1st Lt. Christina Vargas is the lone female in this class) unit to train fellow soldiers. This "train the trainer" approach is the foundation of ACS and helps to ensure consistent methodology throughout the Army.

The students begin a series of drills at the urging of Larsen's "right-hand man" Sgt. Dave Barron, starting with walking neck bridges — picture someone lying on his back, arching it and "walking" around his head. From there it's on to partner-aided back arches, combat rolls and then back to grappling. The grappling drills begin with one student on his back and his opponent straddling him in what's known as the mount position. From here, they flow through a series of traps and escapes until the roles are reversed and the drill is repeated.

"Fighting is all about moving right," Larsen says. "It's like kinetic chess. The goal is to instill movement patterns that become instinctual."

Larsen wants his instructors — all of whom have seen time in Iraq or Afghanistan — to be able to react without thinking or hesitating so they can pass that on to their students. Students must fully commit to the training, or risk their lives or the lives of those they serve with.

But the benefits of this type of training also trickle into the realm of fitness. Intense grappling can burn up to 800 calories an hour and builds remarkable endurance. According to Larsen, the typical soldier will drop 15 pounds during a four-week summer course, when the temperatures routinely climb into the triple digits. Today the thermometer reads 101 degrees F, but that doesn't account for humidity, which, according to weather.com, hit 69% at 11 a.m. Here I stand, taking notes, my polo shirt drenched with sweat, wondering how they train this way for eight hours a day. There's no overstating the importance of water — or deodorant — in here.

Sgt. Barron calls the class up for a short refresher on kick defense, going through five different ways to avoid getting a boot print on their faces. The first tactic, evasion, is presented with matter-of-fact, if not comical, eloquence: "The best way to not get kicked? It's to not be there."

The students break into twosomes again, taking turns kicking and defending. Master Sgt. Fletcher looks in on a pair on the mat just in front of us before stepping in to correct them. "What are you doing? That's not realistic. You signed up to get kicked!" he reminds them. Needing little more encouragement, the two students return to pounding each other about the shins and thighs with purpose.

1245 FEAR FACTOR

Larsen sees fear as one of the most effective tools in ACS — it's the one thing that separates his brand of mixed martial arts drills from those done in rank-and-file fight studios across the country. But the fear of heading through the fatal funnel or riding in a Humvee with a handful of angry detainees is impossible to simulate here at Fort Benning, so the instructors have to get creative.

As in many of the drills throughout the first half of the morning, soldiers are paired off at different parts of the mat. Before assuming dominant or submissive positions, as is custom for their grappling drills, they're ordered to close their eyes and face the outside of the room. Sgt. Barron then walks around the room and quietly drops a live stun gun into the low-set pants pocket of one of the soldiers. The only one who knows that there's a weapon in play is the one who has it, heightening the intensity of the drill. On a regular day in the gym, a bad set results in a subpar pump — you reset your headphones and get back after it in a minute. Here at ACS, have a bad round on the mats with a stun gun in play and you could be looking at 100,000 volts in your ribs.

After the instructor covertly places the stun gun, students return to the submissive-dominant position. As they get started, it becomes clear that the fighting is much more intense here than in earlier exercises. Students approach the drill as if their opponent is an armed enemy. The goal is to control them, to keep them from reaching for a weapon. A scream from one corner of the room is accompanied by a tight-faced grimace — someone has been eliminated and the action is halted by Sgt. Barron. Sometimes the student with the stun gun wins out, but other times he or she is overtaken and stunned themselves. This drill is repeated over and over, with the loser of each pairing sent off to the side, narrowing the field until only two soldiers remain. The final two students begin in usual fashion but neither has the weapon. It's only after several minutes that it's introduced, placed just out of reach of both soldiers. On this day, Staff Sgt. Jason Alford gets to it first and zaps his opponent.

"It's a great training tool because it's electric, so you're scared of it," Alford says. "You're more scared of that than getting choked out."

"Most of the fights today are over weapons," Larsen says. "So this is pretty typical of the kinds of things that happen in combat, which is why it's so effective. Noted firearms instructor and author Massad Ayoob said, 'At close range it's not a shooting contest; it's a fight.'"

Students, some of whom are accomplished professional mixed martial artists, are further motivated by contests held throughout the year. Staff Sgt. Stelly has twice turned down offers to fight on Ultimate Fighting Championship cards, instead opting to deploy with his unit back to Afghanistan, but Larsen sees a fighting future for the Louisiana native.

"He'll be a UFC champion one day, I guarantee it," he says of Stelly, a former Georgia state amateur boxing champ and the All-Army Combatives heavyweight champion in 2005. Stelly also won the 2002 Sambo World Championships after having practiced the esteemed Russian martial art for all of two weeks. In nine professional fights on the MMA circuit as of press time, Stelly has lost only twice.

When asked if he sees himself making a living in the cage someday, Stelly, polite and modest, simply points to the time remaining on his enlistment. "Two years, then we'll see." Duty first, soldier.

1740 FIGHT CLUB

The instructors at ACS are not the sort you want to piss off. The practical strength-focused program developed by Larsen — tire flips, sled drags, kettlebells and the like — has left each of them broad-shouldered and barrel-chested, not to mention quick-fisted. But nothing the students learn at ACS is without a practical military application, which means a commitment to training through pain.

As such, very little gets in the way of the instructors honing their craft. A day missed, they reason, means depriving a student of what is arguably the most valuable skill they can take into a deployment to a war zone.

Staff Sgt. Brandon Brewer is a prime example of that selfless abandon. Today he's getting ready for a customary afternoon full-contact sparring session, but with three broken bones in his right hand — and he's right-handed.

"I'll be fine," he says, slipping in his designer mouthpiece (it reads "Beast") and giving a nod of encouragement to Larsen before his opening round against Staff Sgt. Andrew Chappelle.

These soldiers, who regard black eyes and sore shoulders as the cost of doing business, have a craft to master. There's no time for UFC glory, no time for bones to set and certainly no time for spot-training.

As the hot Georgia sun begins to set, Larsen says that nothing in the world is as hard as training for the combative arts. After a full day's worth of seeing the world's best soldiers spill sweat and blood to prove it, I believe him. M&F

For more information on the Army Combatives School, visit moderncombatives.org