Cold may hold hostages, but it takes no prisoners. Cold retreats, but it signs no armistice agreements. Cold has no conscience, attacking women and children as fiercely as men. It slams you from all sides, infiltrates any hole in your defense, seizes extremities, penetrates to the core of your being. Cold is silent as a shadow, deadly as a bullet, relentless as a new missionary.

Cold is more treacherous than heat because it turns your body against you. When things get hot, clothing comes off to prevent overheating. But when the temperature falls to single digits, we grunts, we infantrymen, emulate onions. We wear wool and cotton socks inside ungainly vulcanized Mickey Mouse boots. Over skivvies we pull two sets of long johns, heavy wool pants and a shirt, thick cotton-twill field trousers, then a poplin field jacket with insulated lining, and finally a hooded parka with its own fleece liner. Steel helmets cover fur-lined pile caps. Scarves are twisted around necks. Thus cocooned while hauling a Garand or a Browning, a load of ammo and sixty pounds of field gear over steep mountains, we are soon drenched in sweat. When we are so exhausted that we can barely stand and word comes to take five, perspiration crystallizes to ice.

Now we must expose our bodies to the elements, change soaking underwear and socks for dry ones — or risk losing toes, or even a foot, to frostbite. Even after such precautions, crotches chafe and blister under the constant friction of the march.

Humping those rugged mountains consumes calories. We are always hungry. Playing at war against the time when such games become real, we eat field rations and hope for one hot meal a day, maybe breakfast. At midday we munch on the march or during brief breaks, prying out a chunk of ham-and-lima-beans or tuna-and-noodles or some other pathetic concoction with the tip of a bayonet, warming it on the tongue until it goes down without frosting the gullet. When we stop for the night, Sterno® thaws cans until we can gulp their half-frozen nutrition. We pack canteens under parkas to keep them from icing.

Despite two years in Southern California, I am a Midwesterner, and after sixteen Chicago winters, I had supposed that the Korean seasons would hold no surprises — after all, Seoul is well south of Chicago. But the peninsula is surrounded by seas that retain heat, elevate atmospheric pressure, trap cold air above the land. The Land Of The Morning Calm is scored by deep mountain valleys between almost parallel ridges running toward Manchuria. Siberian cold barrels down these natural ducts, freezing stubble in the paddies and robust mountain rivers and the tiny hairs inside our noses. Even thinking back to my boyhood and an unexpected urban hike through a Great Lakes blizzard to pay a family debt, nothing I experienced in Chicago came close to preparing me for the Korean winter of 1960-61.

In such cold, coping with bodily functions requires extraordinary effort. Voiding our bladders, the steaming yellow freezes as it reaches the ground. Our sergeants describe fastidious Wermacht soldiers on the Russian Front who pulled down trousers before squatting over slit trenches, then incurred frostbitten anuses that turned gangrenous. We pray for constipation. We hope that daylight will bring warmth enough to find relief without freezing our asses. Sometimes we are forced to emulate the Russians, who knew that filling one’s pants is uncivilized and uncomfortable but probably won't kill you.

Gangrene can kill you. When it doesn’t, you’ll wish that it had.

At dark we fan out by squads to take up defensive positions along a ridge. The wind is a knife and the earth is frozen concrete-hard so we can’t dig in.  We spread ponchos and canvas shelter halves on the ground and climb fully dressed into sleeping bags — but can’t stop shivering long enough to doze off. About 9:00 the thermometer bottoms out near thirty below, plus severe wind chill. In pity, perhaps, orders come down from HQ in Seoul: training is suspended. "Units will implement administrative field procedures," comes the word.

Squad fires are ordered; there is little to burn: Decades of woodcutters from tiny villages crouched in even the most remote valleys have cleared the ridges of trees. The farmers winter in their thatched huts, heating floors with homemade charcoal or the twigs and branches so laboriously cut in autumn.

We grunts circle a pile of stones and after exhausted men haul up jerry cans of diesel, slop it on the stones, light it with our fake Zippos. The wind fans the flames;  two feet away, our hands thaw — but our backsides stay frozen. Turning back-to-front every ten minutes, no one sleeps. At dawn the fires are extinguished. We return to mock attack, simulated withdrawal, to pretend battle, to our all-too-real war with winter.

Days later we return to garrison, to drafty steel huts barely heated by oil stoves, to rats skittering beneath shaky plywood floors, to latrines and showers dispensing murky, undrinkable water.

To an earthly paradise. 

Dante got it wrong: The damned are not doomed to sweat eternally in a toasty hereafter. Hell, as every grunt who survives a year in the Land of the Morning Calm knows, is almost as cold as Korea.

© 2000 Marvin J. Wolf

I reported to Ft. Benning, GA and was assigned to the Ranger Combat Conditioning Committee. We were attached to the Ranger School, but not part of it, and that was good: Rangers earn their elite status by learning to fight under the most difficult conditions. That meant nine dirty, weary, hungry weeks patrolling swamps and mountains, eating berries, rodents and rattlesnakes and playing at war while supervised by "lane graders" who took pleasure in finding ways to challenge their charges.

My arrival coincided with the first day of a training cycle, when new students, all volunteers, are introduced to the weary weeks ahead. The students assembled in a U-shaped formation and the Ranger sergeant major introduced them to Lightning, his six-foot timber rattler. Then he put a white rabbit into the snake's cage. Lightning coiled. The rabbit froze.  Finally it twitched — and faster than the eye could follow, Lightning struck. The rabbit jerked, twitched, quivered. In two minutes it was dead.

"Before today is over," bellowed the topkick, "Every one of you will handle this killer snake with your bare hands."

At that moment a staff car turned the corner and drew to a halt behind the snake cage. The rear door opened and a tall officer emerged. He wore a lieutenant colonel's silver oak leaves, and the distinctive yellow-on-brown shoulder tab that identified him as a Ranger. He strode angrily toward the formation.

"Sergeant Major, I thought I warned you about trying to scare these men with that sick, old snake," he said.

"No sir, you never said nothing about it," said the sergeant major.

"I ­know­ that snake, and he's had his fangs removed," bellowed Lieutenant Colonel Denham.  "What did you do, put a drop of atropine from a gas mask kit on the rabbit, so he'd go into convulsions?"

"No sir!"

"These men are never going to learn a thing about handling snakes until you use a rattler with all his equipment," said the colonel.

"I'm telling you, Colonel, that Lightning's got ­all­ his equipment.  He's a killer. He'll croak you or me quick as he did that rabbit."

"Bullroar.  I'm no more afraid of ­that­ old snake than I am of the bogeyman."

"Well, if you feel so strongly, Colonel, maybe you'd like to put your money where your mouth is."

I stared at the colonel as if he was nuts. So did every one of the 200 students.

The sergeant major reached into his pocket and took out a wad of bills.

"Right," said Denham. "I'll wager a hundred dollars that I can put my leg in that toothless, sick, elderly, worn-out snake's cage and let him bite it, and be no more bothered than if I was bitten by a mosquito."

"You're on, Sir," returned the noncom.

"How about another on the side? I'll bet every man here a dollar. My two hundred dollars against your one dollar each," said Denham.

"What do you say, Rangers?" bellowed the sergeant major.

The ranks responded with a raucous cacophony of derision.

"Let's get the snakebite kit out here," yelled the sergeant major, and a medic came forward with a canvas bag adorned with a red cross.

"We better let someone hold the bet, because after Lightning bites him, the colonel will be on his way to the hospital," said the sergeant major, looking around. Just then a field ambulance, emblazoned with a huge red cross, turned off the blacktop and onto the gravel street.  The sergeant major stuck two fingers in his mouth and let out a shrill whistle. The ambulance stopped and the driver's head poked out the window.

"Bring that meat wagon over here, Specialist, I'll have a load for you in a minute," bellowed the noncom. The driver rolled up, then unbuckled a canvas stretcher. I stepped out of the shade to see, and the sergeant-major yelled at me to come over.

"This damn-fool has just bet these Rangers a dollar apiece that he's not afraid to stick his leg in the cage with Lightning. Will you hold the bet, young sergeant?" he said.

I was speechless.

"Won't take a minute, Sarge. Help us out here." So I walked up and down the ranks, collected a dollar from each man, then took the sergeant major's money. Colonel Denham handed me three crisp hundred-dollar bills.

An almost palpable hush descended on the ranks as Denham strode resolutely toward the wire mesh cage. The sergeant major took out a key, broke open the heavy steel lock, pulled it off the hasp. Then he hesitated.

"You really want to do this, Colonel? Ol' Lightning could kill you."

"I'm not afraid of being gummed by that senile, toothless snake," roared Denham.

The sergeant major shook his head in disgust. He took a big forked stick from the top of the cage, then opened the door a few inches. Someone in a back rank coughed, and then it was dead quiet. Denham put his right leg in the cage.

Lightning had flowed to the center of the cage, where he wound himself into a huge coil. When Denham's leg moved, ever so slightly, the snake struck at the khaki trousers, recoiled, struck again.

Denham didn't even twitch.

The sergeant major forced the huge snake to the rear of the cage with the forked stick, then jammed the lock on the hasp.

Four hundred unbelieving eyes followed Colonel Denham as he strolled over to me and stuck out his hand. I handed him the money.

"Sergeant-major, I'll be back at the end of the course, and I expect to see a healthy, poisonous rattlesnake by then."

The sergeant major's mouth hung open. He snapped his jaw shut and swallowed.

"Yessir," he said.

The staff car rolled up and the driver scurried around to open the rear door. The sergeant major exchanged salutes with the colonel, then turned back to the company.

And as Lieutenant Colonel Ernie Denham, who had left most of his right leg behind in a blazing Sherman tank during the Battle of the Bulge, got into the car, he carefully rolled up his pant leg to reveal the wooden prosthesis that had replaced it.

"See you in nine weeks," he said to the sergeant major, who as a teen-aged PFC had pulled Lieutenant Denham from the burning tank.

The sergeant major turned back to the troops. "Today, Rangers, we have learned about the dangers of making assumptions, the importance of planning, and the powerful effect of surprise,"  he said. He went on to say that after Denham lost his leg, he spent years in hospitals, learning how to walk. He could have retired on a nice pension, and spent his life mourning his lost limb. Instead, Denham fought to stay on active duty. Anybody who ever spent an hour around him would never again believe that having only leg is a handicap if you don't want it to be.

So I'll bet $200 that after stumbling around swamps and mountains for weeks, sore, exhausted, bug-bit and ravenous, what kept some of those 200 students from quitting Ranger School was the thought that one-legged Ernie Denham became a Ranger ­AFTER­ he lost his leg.

© 2000 Marvin J. Wolf

It was late; I adjusted the Coleman® lantern until the mantle barely glowed, checked my M16 on a hook near the door, noted where I’d left my helmet and flak vest, then removed my boots, loosened my belt, and stretched out on the canvas cot. I closed my eyes, let myself drift off.

About eleven the monsoon returned and the roar of raindrops on a sheet tin roof woke me. I set the field phone buzzer to maximum volume. Pulling a poncho liner over myself, I tried to sleep.  I’d been in Vietnam for nine months, however, and had seen terrible things. Sometimes I had nightmares.

Somewhere in the twilight between sleep and awareness, during a lull in the storm, I heard a single Click! from the buzzer — as if some errant electrical impulse had passed through it, perhaps only a single electron, just enough to nudge the striker against the bell once. I pried the receiver from its spring-loaded clamps and put it to my ear.

"First Air Cavalry Public Information Office," I said. “Sgt. W___ speaking.”

A faint voice danced on the crackling line. The static receded and I heard a voice, and then another, tinny but clear and urgent in the darkness.

"Golf Course Tower,"  said the louder voice. "Use two-one right."

The Golf Course was the nearby division airfield.

"Copy two-one right," echoed the fainter voice.  "Got a load of stiffs for the morgue."

Every hair on my body stood up.

"You'll see the field hospital on the right, halfway down the runway. The morgue is just beyond. Taxi over. Try not to blow it down."

 "Hello!" I shouted into the phone. "Golf Course Tower, do you copy?"

I heard only the snap and hiss of an open line. I was on a telephone, and, amazingly, listening to a radio conversation.  How could this happen?  Again I shouted into the mouthpiece. Again I listened.

 "Copy a load of stiffs?" said the Tower.

"Roger.  Nineteen KIA. Mortar platoon got overrun."

My testicles shriveled, my guts churned and I choked back bile. A mortar platoon. A mortar platoon. Oh God, I thought. Not Paul. Not Sam.

The voices faded. I jammed the handset against my ear but heard only static, like grease writhing on a distant grill.

A year earlier, Paul and Marie Harrison had been my next-door neighbors. Paul was the All American Boy, ruggedly handsome, muscular, well grounded in common sense. He laughed often, worked hard, made friends easily.

He got drafted. Soon afterward, for complicated reasons, I decided to re-up.  By chance we both wound up in the First Air Cav. Paul became a mortarman.  I was a combat photographer.

Marie wrote me often, urging me to look after Paul. There was little I could do; he was in a rifle company; I was in PIO. We both spent most of our time in the field. We met twice, spoke on the phone a few times. But Marie wrote regularly; I knew how much she needed Paul.

­A mortar platoon overrun. There were dozens of mortar platoons shi

But if it was — what about Sam Castan?

Sam had appeared four days earlier, at dusk, a slender man in his early thirties. Hardly had he introduced himself when the first Vietcong rocket screeched overhead. A moment later a muffled thud rose from the airfield. Then another screech, and another thud.

We spent the night in a bunker that doubled as my darkroom.

By morning I had come to know an admirable man.  Castan was a rising star at LOOK, the picture-heavy newsmagazine. With his Roman nose, penetrating eyes and open, charming way, Sam was a gifted raconteur.  He made me feel that he'd been everywhere and done everything.   Self-deprecating, worldly, he perched comfortably at History's elbow to record what passed before him with wit and insight.  I saw in Castan exactly the professional that I aspired to become.

The story that brought him to the Air Cav, his own idea, was the effect of a single American death. At that time about 200 GI coffins left Vietnam each week; he wanted readers to see the magnitude of that loss by illuminating the effects of just one death. Sam's plan was to join an operation; if someone was killed, he’d follow the body back for burial, along the way interviewing the deceased's buddies, family and friends.  While treading close to the macabre, Sam felt that his story would provide the profound personal dimension lacking in faceless casualty lists.

I suggested that Castan join a brigade-sized foray called Operation Crazy Horse, set to kick off the next day.  Paul's Charlie Company would be part of Crazy Horse; by escorting Castan I could spend time with both.

But as we were about to leave, my boss, Major Siler called me back.

"Castan’s cherry was popped a long time ago," he said.  "He doesn't need babysitting, and I've got things for you to do around here." Siler had in mind a pile of paperwork that I'd been avoiding for weeks.

I drove Sam to the Twelfth Cav, introduced him to Charlie Company's topkick and hung out with Paul for a bit.  That night I wrote Marie, assuring her of Paul’s good health. 

And now this weird telephone call. I was spooked.

I called Graves Registration, woke an officer and asked what he knew about 19 dead in a mortar platoon.
"This can't wait until morning?" he growled.

I explained about the radio conversation on my field phone. The officer’s voice grew thick with sarcasm.

"Give Major Feldman a call in the morning."

Feldman was the division psychiatrist.

I sat, thinking. Was I nuts? Had the war finally got to me?

I called the Tactical Operations Center and a sergeant I knew. I said I had  an inquiry about an overrun mortar platoon with 19 KIA.  What could he tell me?

He promised to check; when he called back he said that nothing like that had been reported.

I’d been dreaming, I decided.  It seemed real, but it was absurd that I could have overheard radio traffic on a telephone. Worried about Sam and Paul, my mind had played tricks me. Exhausted, I lay down and slipped into deep, dreamless sleep.

The phone rang, loud and clear, and a sergeant with a deep, almost sepulchral voice said he was calling from the morgue. He had a body that he thought might be a civilian.

"Any newsmen you can't account for?" he asked.

I fought for breath, a fish jerked from a lake. The only reporter I knew about was Castan. Calm down, I told myself. Some newsie might have joined a unit in the field without bothering to check in; it wouldn't be the first time.

The morgue sergeant said they’d need an ID on the body. I pulled a poncho over my head and ran a few yards to Siler's hooch.

"I met him for two minutes," said Siler. "You spent hours together. This one's yours." 

The morgue was a mile’s march; my dread grew with every step. From time to time I tilted my face skyward and let falling drops wash away my tears.

My mind cowered behind a wall of numbness as I stepped inside the morgue tent and identified myself to a staff sergeant.  He shook out the contents of a plastic bag.

"Recognize any of this?" he said.

I saw Hong Kong coins, keys, a folding knife and a Zippo lighter engraved with the ­LOOK­ Magazine logo. On the other side were initials: S. C.

"Might be Castan's lighter," I said.

I followed him down a canvas corridor to a  chamber cluttered with wooden tables.  Naked bulbs dangled from overhead cords. Each table had a body bag.  The sergeant consulted a zipper tag, glanced at me,  opened the bag halfway and stepped back. Somebody moved in behind me to work over another body. Squinting, I hunched forward.

Sam.

I was empty, spent, unutterably weary. ­Why Sam? What a waste­, I thought. I tried to pull myself together.

"That’s Castan.”

"Need you to sign the death certificate, identifying him," he said.

Turning to leave, I glanced at a body on the table: Paul Harrison. Gruesome wounds marred his chest, limbs and abdomen but his face was unmarked and strangely peaceful. A sergeant put two pieces of paper in front of me, and I signed them. I don't remember walking back or telling Siler what  happened, but somehow I did.

Later I learned a little about how Sam and Paul died:  Helicopters had dropped Charlie Company on LZ Hereford, a jungled slope 20 miles east of our basecamp. As the rifle platoons moved down the mountain, looking for the enemy, the mortars remained to support their advance.

But in the thick elephant grass just above Hereford waited 100 heavily-armed men of the North Vietnamese Army, so well concealed that the rifle platoons passed right by them. When these platoons were far down the mountainside, out of sight, the NVA fell on the lightly-armed mortarmen. They radioed for help but by the time the rest of Charlie Company returned, the fight was over. Three badly wounded men hid in thick brush; everyone else was killed.

Several weeks later another Air Cav unit fought this same NVA regiment; among the gear and equipment we recovered from the battlefield were Sam's  cameras and exposed film. Sam’s last photos included several of a mortarman using a bayonet and a shovel in desperate hand-to-hand combat.  The very last exposure shows this soldier’s death:

It was Paul.

When I returned from Vietnam, I went to see Marie and her toddler daughter.  Many years later we reconnected. Marie was still teaching third grade. She had remarried and borne a second daughter, but I soon realized that as much as Marie learned to love her second husband, she never entirely got over Paul's loss. We stayed in touch until her death two years ago.

Memories of Sam haunted me for decades. I felt complicit in his death; if I hadn’t wanted to see Paul, Sam would have accompanied another unit.  With the arrival of the Internet and other research tools, I discovered that Sam had shortened his name from Castagna and that a plaque in New York's Overseas Press Club honors his memory. I wondered how his death had affected his wife, Frances, who had remarried and was known as a gifted poet and writing teacher.

Thirty-three years after Sam’s death, I was finally able to meet Frances. I told her how Sam found himself at LZ Hereford and asked her forgiveness for sending him to his death.

"There’s nothing to forgive," she said. "You couldn't know what would happen and you only were trying to help Sam."

I had told that to myself for years, but I needed to hear it from Frances. A great burden lifted from my soul.
Only then did I stop dreaming about my awful night in the morgue, and only then did it occur to me that if Siler hadn't prevented me from escorting Sam, surely I would have died with him at Hereford.

I don't know if I’ll ever find meaning in the lives of those who died in Vietnam, but from Marie and Frances I learned that hearts heal and lives go on.   I have researched radio phenomena and learned how it was possible to pick up nearby radio transmissions on a telephone, especially in wet weather.

But  I will never understand how, at precisely the moment when a  pilot radioed the tower that he was bringing Paul and Sam's bodies to the morgue, a single chirp from my telephone summoned me to listen.

© 2000 Marvin J. Wolf

When my turn for R&R came, I chose Hong Kong, primarily because my photographer pals assured me that shopping for cameras there was cheaper and required less hassle than in Tokyo.

After a few hours of air-conditioned splendor, our 707 charter dropped down out of the clouds, threading the gap between mountains and skyscrapers to land with a roar at Kai Tak Airport. I might have found the approach exciting if I hadn’t made too many assault landings in C-130s.

Herded off the plane, we were whisked through Customs and onto Army buses, officers on one, senior noncoms on another and the rest of us enlisted swine on the third.  We drove slowly past a row of hotels, stopping at each as a  beefy Special Services—not to be confused in any way with Special Forces—noncom bellowed out hotel room prices, meanwhile suggesting that the lower-ranking among us should choose one such place or another. I remained until there was no one but me and the burly Special Services sergeant.  “What are you waiting for, the Ritz?” he bellowed.

I strode the length of the bus and sat down in the front row.

“I wanted to ask where you’d stay, if you were here for a few days and didn’t want to be around a bunch of drunken snuffies dragging whores up and down the hallways all night long,” I said.

He looked at me like a long-lost brother.

“A man after my own heart,” he said. Ten minutes later he dropped me at a backstreet Kowloon hotel; after a shower and a late lunch I found the camera store that Henri Huet had suggested and spent the rest of the afternoon happily trying to decide what to buy on my limited budget. I came away with two Nikon lenses, a tiny, half-frame Olympus with wide-angle lens, and, because PIO’s aged Remingtons were worn-out relics, an Olivetti portable typewriter.

After dropping my treasures at the hotel I was ready to play.  Sure, I wanted a girl.  Hell, I needed one. But I had done my homework, interviewing several guys  returned from Hong Kong; I was looking to avoid the flocks of whores working the R&R hotels and the Suzie Wongs bleeding sailors in the storied bars of the Wan Chai District. Surely, I thought, there had to be at least a few Hong Kong girls who could sustain the illusion of a doomed romance for three or four days.

I found her the next day in an out-of-the-way restaurant in which my fair hair and pink skin stood out. She was dining with several half-grown children, running back and forth to fetch them dishes from the kitchen with an easy familiarity and when I caught her eye she gave me a dazzling smile.

I started for her table but she intercepted me. “Not here,” she murmured, pressing a card into my hand.  The card directed me to exactly the sort of  Nathan Road bar that I’d been avoiding: loud, smoke-filled and crawling with girls dedicated to vacuuming the pockets of visiting American servicemen. 

She called herself Caroline Lee— not her real name, I’m sure—and she was really quite special for a working girl anywhere—and I don’t mean just her looks.  We spent three lovely mornings sight-seeing and hand-holding; afternoons she disappeared for several hours—perhaps, as she explained, to care for an extended family that included siblings, elderly parents, an aunt and young cousins—and then found a good restaurant for a leisurely meal, followed by a night of gentle sex and much holding. I’m not sure which I needed more.

Her story, which even then I supposed might have been partly true, was that, desperate for money to support her siblings when their parents died, she had gone to work in a bar.  Finally she had saved enough, with partners, to open a restaurant—but still needed to work as a bar girl several nights a month. With such a history, marriage to a respectable Hong Kong man was out of the question. A GI had proposed to her, she said, but she couldn’t leave her family and move to America.

We parted as old friends; I gave her the sum she’d asked for and all my remaining my cash. On the flight back to Vietnam I regretted not taking her address, before accepting that I would never know what became of her.

Later, back at Tansonnhut and drowning in the stifling heat, crushing humidity and stomach-churning stench of jet fuel, I waited hours for an up- country flight. Returning from a latrine call I found a young GI, dressed in civvies for R&R, squirming with anticipation in the next chair. He was perhaps nineteen, fair hair cropped close—a strapping, eager kid from the Big Red One, the First Infantry Division, who wanted everyone to know that he’d volunteered for an extra ninety days on LRRP—long range recon patrol—just to get a second R&R and return to Hong Kong and the girl he’d met there.

Before I could refuse he thrust a packet of photos at me. I recognized with a start the colorful logo on the envelope as twin to one in my AWOL bag. He pulled out pictures of his Hong Kong fiancée, the girl he was going to marry and take back to Kansas or Oklahoma or some such place—and I found myself looking at the lush curves, the long, shiny dark hair, the flawless olive skin, Eurasian eyes and the slightly off-kilter and unmistakable nose of Caroline Lee.

“Her name is Caroline,” he gushed. “Isn’t she beautiful?”

He’d met her on her very first day as a hostess in a bar on Nathan Road, he said, and he’d  been sending money every month so she wouldn’t have to work there. His Mom was okay with him marrying a Chinese girl who might be a little bit Portuguese on her mother’s side. He didn’t care if she’d maybe been with another man before they met because she was special. They were in love.

“Very pretty,” I said, biting my tongue and agonizing over what, if anything, I should tell him. I settled for keeping my mouth shut and hoping that when he got to Hong Kong he wouldn’t be able to find the lovely Caroline.

It was a long flight back to An Khe.
© 2001 Marvin J. Wolf