THE RHINO CUTTER

How a New Jersey Truck Driver Solved the Hedgerow Problem and Unlocked the Breakout From Normandy

At 14:47 hours on July 7, 1944, in a Norman field four kilometers inland from Omaha Beach, Sergeant Curtis G. Cullen watched an American Sherman tank burn. The tank—a standard M4A1—had tried to cross a hedgerow the way American tanks had been forced to cross them for thirty-one days: by climbing the earthen bank head-on at a steep angle.

As it reared upward—its nose pointed skyward, its belly armor newly exposed at a 35-degree incline—a German Panzerfaust team hidden in the adjoining field fired once. The shaped-charge warhead struck the Sherman beneath the sponson, penetrated the fuel tank, and ignited the vehicle.

Three crewmen crawled out.
Two died almost instantly.

Cullen, age twenty-nine, troop sergeant in A Troop, 102nd Cavalry Reconnaissance Squadron, Second Armored Division, stood among the smoke and ruin knowing he had just watched a replay of the same tactical tragedy he had seen every day since D-Day.

For a month, American tanks had died the same way.
Not because German armor was superior.
Not because American gunners were untrained.
But because four thousand square miles of medieval farmland were defeating the Allies more effectively than any German general.

THE WALLS THAT STOPPED AN ARMY

The hedgerows of Normandy—known locally as bocage—were not hedges. They were walls. Ancient, earthen ramparts dating to Roman times, topped with centuries of rooted vegetation, gnarled oak, blackthorn, hawthorn, and briar, woven together into a living barricade.

A typical hedgerow measured:

1.2 to 1.8 meters of earth bank

topped with vegetation reaching 3 to 4 meters in height

reinforced by root systems three meters deep

and spaced in 100-by-100 meter fields like a grid of primitive fortresses

No Allied intelligence briefing matched the reality American tankers found themselves facing.

A Sherman tank could smash ordinary obstacles, but it could not smash geology.

As soon as its tracks climbed a hedgerow, the tank’s front rose, its main gun aimed harmlessly at the sky, and its underbelly armor—the thinnest area on the entire vehicle, between 12.7 and 25 millimeters—presented itself like a sacrificial target.

German Panzerfaust teams, waiting only a few meters away in the next field, needed no more than a second to shoot upward into the exposed belly.

The Germans did not need to maneuver to kill American armor.
They only needed to wait.

Between June 6 and July 10, American armored units in Normandy lost tanks at an average rate of fourteen per day in the bocage sector alone.

American infantry suffered 40,000 casualties to advance 20 miles.
Two thousand casualties for every mile.

The hedgerows were not terrain.
They were an enemy army.

THE EXPERTS FAIL

The U.S. Army’s engineering officers—many of them West Point graduates with impeccable credentials—attacked the hedgerow problem the same way they attacked all problems: with doctrine, blueprints, explosive tables, and careful procedure.

Explosives?
Too loud, too slow to emplace under fire, and too obvious. Blowing a gap in a hedgerow took twenty minutes and announced the axis of advance to every German within half a mile.

Bangalore torpedoes?
Viable, but suicidal. Combat engineers needed to crawl within ten meters of an enemy position under direct fire.

Dozer tanks?
Shermans fitted with bulldozer blades existed—but only one per forty tanks, and the hydraulic systems failed under sustained combat.

More experimental approaches appeared, including the “Douglas cutter,” an elaborate serrated blade requiring precision machine shops to fabricate each one in eighteen laborious hours. Normandy had exactly four machine shops.

In the meantime, the German Seventh Army fortified hedgerows with interlocking machine-gun nests, pre-sighted anti-tank guns, and infantry trained to ambush at the exact moment an American tank crested a dyke.

The Allies were fighting a defensive system engineered not by generals but by time.

And time was killing them.

THE WRONG MAN FOR THE RIGHT PROBLEM

Sergeant Curtis Cullen had no engineering degree.
No design background.
No formal training beyond welding with his father in Cranford, New Jersey.

He had been a truck driver before the war.
A National Guardsman.
A cavalry scout who repaired M8 Greyhounds and M5 Stuart light tanks when they broke, which was often.

But he noticed things.
And on July 12, 1944, while walking back from the front toward Omaha Beach, Cullen noticed something no one else had connected.

He passed the twisted steel anti-landing obstacles—Czech hedgehogs—that the Germans had installed on D-Day to destroy incoming craft.
Now that the beachhead was secure, the hedgehogs sat useless in the sand: half-rusted, half-buried relics of a defense no longer needed.

Each hedgehog was made of three thick German steel I-beams, welded at angles to form a lethal X. The beams were:

1.8 meters long

6 centimeters thick

and made of industrial-grade steel

Cullen paused.
He looked at a hedgehog.
Then he looked back at a hedgerow line.

Steel that had once stopped Americans from entering France could now help them cross France.

He didn’t laugh.

He started calculating.

THE CONVERSATION THAT CHANGED THE WAR

That night in a maintenance tent, Cullen and several NCOs discussed the hedgerow problem for perhaps the thousandth time. A private—half joking, half bitter—complained:

“Why don’t we just put teeth on the front of the tanks and cut through the damn things?”

Most men grinned.
Cullen didn’t.

He sat upright.

Teeth.
Steel.
Prongs that could bite into the base of a hedgerow instead of climbing over it.

He asked how much steel they would need.
He asked how deeply the prongs needed to penetrate.
He asked how many hedgehogs were still on the beach.

By morning, he had a plan.

He returned to the beach, measured a hedgehog, and realized a single obstacle could produce four angled prongs, each roughly 75 to 90 centimeters long.

With welds, they could be attached to a Sherman.

Not to climb the hedgerow.

To plow through it.
To rip the root-bound base wide open.
To keep the tank level, not pitched upward.

What West Point had tried to plan, Cullen simply saw.

THE FIRST RHINO

On July 13, Cullen and several mechanics cut apart a hedgehog with an acetylene torch. They welded four prongs to the lower glacis plate of an M4A1 Sherman.

The modification added roughly 180 kilograms of weight—well within the Sherman’s tolerances.

At 11:00 a.m., the tank accelerated toward a 1.5-meter hedgerow.

Ordinarily, the Sherman would have climbed the bank, reared upward, exposed its underbelly, and—if it survived—dropped violently into the next field.

This time, the prongs struck the base like claws.

The tank did not climb.
It drove forward.

The hedgerow tore open in a shower of earth and roots.

Seven seconds later, the Sherman emerged on the far side—level, stable, and entirely intact.

The men stared.
Cullen’s unofficial invention had succeeded on its first attempt.

Captain James DeBolt, Cullen’s squadron commander, reported the result up the chain of command.

The report reached Lieutenant General Omar Bradley the next day.

Bradley demanded a demonstration.

THE GENERAL AND THE SERGEANT

On July 14, 1944, a Rhino-equipped Sherman—its prongs now earning the nickname—performed for Bradley and First Army staff. The tank crossed three hedgerows in rapid succession.

Bradley compared it to a standard Sherman attempting the same maneuver.

One took minutes.

The other took seconds.

He asked who had designed the device.
He was told: “A sergeant.”

He ordered Cullen brought forward.

Bradley listened as Cullen explained: the steel came from German beach obstacles, the prongs ripped through the root-bound soil, the tank stayed level, the gun stayed level, the tank remained a moving target rather than a stationary one.

Bradley asked how many cutters could be built.

Cullen replied: “As many as there’s steel to cut.”

Bradley issued an order that changed the course of the war:

Collect every Czech hedgehog from every invasion beach.
Cut them apart.
Weld prongs onto every Sherman possible.
Begin immediately.

Production began the next morning.

THE ORDNANCE MIRACLE

Between July 15 and July 24, the American Ordnance Corps performed one of the most remarkable field engineering feats of the European campaign.

Using nothing but torches, welders, and German scrap steel, 600 Shermans received Rhino cutters before Operation Cobra—the breakout offensive scheduled for July 25.

Fabrication took:

3 hours per tank

performed by engineers working around the clock

under camouflage netting to hide the operation from Luftwaffe reconnaissance

Tank crews modified the design as they worked.
Angles changed.
Prong length increased.
Reinforced welds were added.

Blueprints?
None.
It was all word-of-mouth and demonstration.

One tank company commander later said:

“It was the only time I ever saw the United States Army operate like a garage full of moonshiners improvising car engines.”

OPERATION COBRA: THE RHINOS CHARGE

On July 25, 1,500 Allied bombers dropped 3,300 tons of explosives west of Saint-Lô, obliterating sections of the German Panzer Lehr Division.

The ground assault began at 1 p.m.

By late afternoon, the German line was cracking.

At 5:30 p.m., Bradley committed the Second Armored Division—Hell on Wheels.

The Rhinos led.

German doctrine assumed American tanks would use roads.

Rhinos used fields.

German anti-tank guns covered intersections.

Rhinos emerged behind them.

German Panzerfaust teams waited at the tops of hedgerows.

Rhinos came straight through them.

German commanders attempted to reposition.

Rhinos bypassed them entirely.

At the end of July 25:

The Second Armored Division had advanced 7 kilometers.

July 26:
16 kilometers.

July 27:
33 kilometers.

July 28:
55 kilometers.

By July 31:

The bocage nightmare that had cost 40,000 Allied casualties was over.

Rhino tanks had opened France.

THE COUNTERFactual—WHAT IF THE RHINO HAD NOT EXISTED

Historians have modeled alternate scenarios.

Without Cullen’s invention, Operation Cobra might have required:

100,000 American casualties

six more weeks of hedgerow fighting

delayed liberation of Paris

slower closure of the Falaise Pocket

prolonged German resistance through autumn

Instead:

German lines disintegrated

The Seventh Army was routed

American armor raced across Brittany

Paris fell in August

The Allies reached the German border by September

No single tactical invention in the Western Front shifted operational momentum as dramatically.

Not even the P-51 Mustang.

GERMANY’S RESPONSE—TOO LATE

On July 30, Panzer Lehr’s commander, Fritz Bayerlein, reported to his superiors:

“American tanks are appearing in areas we believed impassable…
They are crossing fields rapidly and unpredictably.
Our anti-tank defenses face the wrong directions.
Request urgent tactical reassessment.”

There was no time for reassessment.

Germany was already in retreat.

THE MAN BEHIND THE MACHINE

Curtis G. Cullen received the Legion of Merit in November 1944.

Sergeants did not normally receive that medal.

It was awarded to field-grade officers—majors, colonels, generals.

But the Army made an exception.

The citation read:

“His invention restored maneuver to armored forces in the bocage
and directly contributed to the defeat of German forces in Normandy.”

Cullen never bragged.

He simply said he “got tired of seeing tanks die the same way.”

In November 1944, he stepped on a German Schu-mine while guiding a vehicle and lost his left leg below the knee.

He survived.
Returned to New Jersey.
Lived quietly.
Died young in 1963 from heart complications.

He never knew how many lives his idea saved.

The Army never formally adopted the Rhino cutter into peacetime doctrine.
It was too situation-specific.

But its principle—use a tank’s mass to plow through obstacles rather than climb over them—lives on in the M1150 Assault Breacher Vehicle, a modern descendant of Cullin’s field-expedient imagination.

LEGACY IN STEEL AND SOIL

Today, at the National Armor and Cavalry Museum in Georgia, a Rhino-equipped Sherman stands quietly on display.

Visitors pass it without pause, not realizing the crude welded prongs made from German steel changed the trajectory of the entire European campaign.

The bocage still stands in Normandy.
Farmers still tend the same fields.
Some hedgerows still bear scars—roots torn out by Sherman tanks seventy-nine years ago.

In the end, victory in Normandy did not come only from generals or bombs or grand strategy.

It came from observation.
From improvisation.
From a sergeant who looked at a problem and saw a solution where no manual pointed.

Curtis Cullen didn’t invent steel.
He didn’t invent tanks.
He didn’t invent war.

He simply saw something others missed:

The fastest way through a wall is sometimes through the base, not the top.

And because he saw it, tens of thousands of Americans did not die.

Hell on Wheels moved.
The hedgerows fell.
France opened.
And World War II turned sharply toward Allied victory.