River crossing

1. Lead

The river as a wall

A river crossing is a military operation in which an army crosses a river in the face of enemy opposition, and it is one of the most difficult operations in war. A river is a natural wall: it stops tanks, it channels infantry into a few crossing points, and it exposes the crossing force, for the minutes or hours that it is in the water, to the full fire of the defenders on the far bank.

The army that is crossing is at its most vulnerable in the middle of the river, with its men in boats, its tanks on rafts, and its engineers building bridges under fire, while the army that is defending is at its strongest, with its guns registered on the crossing points and its reserves ready to counterattack the bridgehead before it can grow.

The history of river crossings is a history of ingenuity and of courage: of pontoon bridges built in the dark, of assault boats crossing under fire, of paratroops dropped behind the river to seize the far bank, and of engineers who, again and again, built the bridges on which the fate of campaigns depended.

Why rivers decide campaigns

Rivers decide campaigns because they are the lines on which armies defend and the lines that armies must cross to advance. In Europe, the great rivers — the Rhine, the Danube, the Dnieper, the Don, the Volga — have been, for centuries, the frontiers of empires and the lines on which wars have been fought.

An army that holds a river line can defend a long front with few troops, because the river does the work of a fortification. An army that must cross a river must concentrate its force at a few points, and it must do so under fire, and if it fails, its offensive is stopped.

The great river crossings of history — Caesar’s crossing of the Rubicon in 49 BC, Napoleon’s crossing of the Berezina in 1812, the Allied crossing of the Rhine in March 1945 — were all turning points, and they were turning points because the river, once crossed, could not be uncrossed: the army that had crossed it was on the far side, and the war had entered a new phase.

2. Key Facts

Definition	A military operation to cross a river in the face of enemy opposition, to establish a bridgehead on the far bank
Phases	Reconnaissance and deception; the assault crossing (infantry in boats); securing the bridgehead; building bridges; passing the main force and its heavy equipment across
Classic examples	Caesar crosses the Rubicon, 49 BC; the Berezina, November 1812; the Dnieper, 1943; the Rhine (Operation Plunder), March 1945
Key troops	Combat engineers (who build the bridges and ferry the troops), assault infantry, and airborne troops dropped behind the river
Key equipment	Assault boats, pontoon bridges, Bailey bridges, amphibious vehicles, and, in the Second World War, the DUKW
Greatest danger	The counterattack on the bridgehead, before the bridges are built and the heavy weapons are across

3. Background

Why rivers are hard to cross

A river is hard to cross for three reasons, and each of them has shaped the history of river crossings. The first is that a river is a physical obstacle: it is wide, it is deep, it flows, and it cannot be crossed by tanks or by wheeled vehicles without a bridge or a ferry.

The second is that a river is a tactical obstacle: it forces the crossing army to concentrate at a few points — the fords, the bridges, the places where the banks are low — and those points are known to the defender, who can register its artillery on them and can mine them and can defend them with a fraction of the force that would be needed to defend an open front.

The third is that a river is a psychological obstacle: the men who cross it know that, once they are on the far bank, they cannot retreat across it quickly, and that if the crossing fails, they will be trapped.

The river crossing is, for these reasons, an operation that requires, above all, preparation: the reconnaissance of the crossing points, the deception that hides the real crossing point from the enemy, the engineers who can build a bridge in hours, and the infantry who can cross in boats, in the dark, under fire, and hold the far bank until the bridges are built.

The river in the history of war

Rivers have been the lines of war for as long as there has been organised war. In the ancient world, the Rubicon was the frontier between Italy and the Roman province of Gaul, and Caesar’s crossing of it, on 10 January 49 BC, was an act of rebellion against the Roman Senate, and the beginning of the civil war that made him the master of Rome.

The phrase “crossing the Rubicon” has entered every European language as a synonym for a decision from which there is no turning back, and it is a reminder that a river crossing is, as often as not, a political act as well as a military one.

In the Middle Ages, the rivers of Europe — the Rhine, the Danube, the Thames — were the lines on which kingdoms defended themselves, and the bridges across them were among the most fought-over places in Europe. In the modern age, the river crossing became an engineering problem, and the armies that could solve it — that could build a bridge in a night, under fire — were the armies that won.

4. Opposing Forces

The crosser and the defender

A river crossing is a contest between two forces with opposite advantages. The crossing force has the initiative: it chooses the time and the place of the crossing, and it can deceive the defender about where the crossing will be made.

But it is vulnerable while it is crossing, and it must, in the first hours, fight with infantry alone, without tanks, without artillery and without supplies, because the heavy equipment cannot cross until the bridges are built. The defending force has the advantage of the ground: it holds the far bank, it has its guns registered on the crossing points, and it has its reserves ready to counterattack the bridgehead.

But it does not know where the crossing will be made, and if it guesses wrong, its forces will be in the wrong place, and the crossing will succeed before it can react. The table below sets out the two sides at the Rhine crossing of March 1945, the largest river crossing of the Second World War.

The Rhine, March 1945: the two sides

	Allies (crossing force)	Germany (defending force)
Strength	About 1 million men in the armies that crossed the Rhine in March 1945	About 300,000 men on the east bank, in shattered divisions, short of men and equipment
Crossing points	Remagen (Ludendorff Bridge, captured intact, 7 March); Wesel (Operation Plunder, 23 March); Oppenheim (Patton, 22 March)	The Rhine line, defended by the remnants of Army Group B and Army Group H
Engineers	Thousands of combat engineers, with pontoon bridges, Bailey bridges and assault boats	Few engineers; the bridges had been blown, except at Remagen
Air support	Complete Allied air superiority; airborne divisions dropped behind the Rhine (Operation Varsity)	Luftwaffe almost absent; few aircraft flying
Commander	Field Marshal Bernard Montgomery (Plunder); General Omar Bradley (Remagen); General George S. Patton (Oppenheim)	Field Marshal Walter Model (Army Group B)

The table shows why the Rhine crossing succeeded: the Allies had overwhelming superiority in men, in engineers and in the air, and the Germans, whose armies had been shattered in the fighting in the west, could not defend a river line 500 kilometres long with the forces they had left. The Rhine, which the Germans had believed to be their last line of defence, was crossed in three places in the space of two weeks, and the war in the west was, in effect, over.

5. The Battle

The Rubicon, 10 January 49 BC: the crossing that made an empire

The most famous river crossing in history was also the simplest. On 10 January 49 BC, Julius Caesar, at the head of a single legion, the Thirteenth, crossed the Rubicon, the small river that marked the boundary between Italy and the Roman province of Cisalpine Gaul.

The crossing was an act of treason: a Roman general was forbidden, by law, to bring his army into Italy, and Caesar, by crossing the river, declared war on the Roman Senate and on his rival, Pompey. The river itself was no obstacle — it was a small stream, and it could be crossed on foot — but the crossing was a political act, and it was, as Caesar himself is said to have remarked, a matter of “the die is cast”.

The civil war that followed lasted four years, and it ended with Caesar as the master of Rome, and with the Roman Republic, in effect, at an end. The Rubicon is a reminder that a river crossing is not always a matter of engineering: sometimes, the river is a line on a map, and the crossing of it is a decision, not an operation.

“The die is cast”

Caesar is said to have quoted the Greek playwright Menander as he crossed the Rubicon — “let the die be cast” — and the phrase has become, in every European language, the expression for a decision that cannot be undone. Whether Caesar actually said it is uncertain: the story comes from the historian Suetonius, writing more than a century later, and it may be an invention. But the phrase has survived, because it captures the truth about river crossings: once the army is on the far bank, there is no going back, and the commander who has crossed must win, or lose everything.

The Berezina, November 1812: the crossing that saved an army

The most desperate river crossing in history was the crossing of the Berezina, in November 1812, during Napoleon’s retreat from Moscow. The Grande Armée, reduced to a starving mob, had to cross a river that was partly frozen and partly open, under fire from the Russian army, on bridges built by Dutch engineers who worked in the freezing water and died at their task.

The crossing, on 26–29 November 1812, saved the remnants of the army — Napoleon himself crossed, and about 30,000 to 40,000 men got across — but tens of thousands of stragglers were left on the far bank when the bridges were burned, and they were killed or captured by the Russians.

The Berezina is the classic example of a river crossing made under the worst possible conditions: in winter, under fire, with no time and with no proper equipment, and it succeeded, barely, because the engineers built the bridges and because the army, for all its suffering, still had the discipline to cross them in order.

The word “Berezina” entered the French language as a synonym for disaster, and it remains so today.

The Rhine, March 1945: Operation Plunder

The largest river crossing of the Second World War was the Allied crossing of the Rhine in March 1945. The Rhine was the last great natural obstacle between the Allied armies and the heart of Germany, and the Germans had blown every bridge across it — except one.

On 7 March 1945, American troops of the 9th Armored Division found the Ludendorff Bridge at Remagen still standing, and they crossed it, under fire, and established a bridgehead on the east bank. The bridge collapsed ten days later, on 17 March, after German bombing and shelling, but by then the Americans had built pontoon bridges and had passed tens of thousands of men across.

On 22 March, General George S. Patton’s Third Army crossed the Rhine at Oppenheim, south of Mainz, in a surprise crossing made without artillery preparation, and on 23 March, Field Marshal Montgomery’s Twenty-first Army Group launched Operation Plunder, the set-piece crossing at Wesel, with a massive artillery bombardment, with assault boats, and with two airborne divisions — the British 6th and the American 17th — dropped behind the Rhine in Operation Varsity, the largest airborne operation of the war.

Within two weeks, the Allies had more than a million men across the Rhine, and the German armies in the west, encircled in the Ruhr, surrendered in April. The Rhine crossing was the last great river crossing of the war, and it was the crossing that ended it.

6. Turning Point

Remagen, 7 March 1945: the bridge that was not blown

The turning point of the Rhine crossing, and of the war in the west, came on 7 March 1945, when American troops found the Ludendorff Bridge at Remagen still standing. The bridge was supposed to have been blown by the Germans, but the demolition charges failed, and the Americans, under Lieutenant Karl Timmermann, ran across it, under fire, and took the far bank.

The crossing was an accident — the Americans had not planned to cross at Remagen, and they had not expected to find a bridge — but it changed the course of the campaign. General Dwight D. Eisenhower, the Supreme Commander, ordered the bridgehead to be exploited, and within days the Americans had passed five divisions across the Rhine at Remagen, while the set-piece crossing at Wesel was still being prepared.

The bridge at Remagen was, in the words of one historian, “worth its weight in gold”, and its capture is still studied as an example of how a single act of courage, by a junior officer and his men, can change the course of a war.

The airborne drop behind the river

The second turning point in the Rhine crossing was Operation Varsity, the airborne drop of 23 March 1945, in which two divisions — about 16,000 men — were dropped behind the Rhine, to the east of Wesel, to seize the high ground and to prevent the Germans from counterattacking the bridgehead.

Varsity was the largest airborne operation of the war, and it was, by the standards of airborne operations, a success: the paratroops landed, they took their objectives, and they linked up with the troops crossing the river within hours. The operation was also costly: the airborne divisions lost about 2,500 men killed, wounded and missing, in a single day, and the debate about whether the drop was necessary — whether the river crossing could have succeeded without it — has continued ever since.

But Varsity showed, for the first time on a large scale, that a river crossing could be made from both sides at once: from the river, by boats and by bridges, and from the air, by paratroops, and that the defender, attacked from two directions at once, could not defend both.

7. Casualties and Losses

The price of the crossing

River crossings are expensive, and their casualties are heaviest in the first hours, when the assault infantry are in the boats and on the far bank without support. At the Rhine, in March 1945, the Allied casualties in the crossing operations were, by the standards of the war, light — about 5,000 men killed, wounded and missing in the Plunder and Varsity operations, and a similar number at Remagen and Oppenheim — because the Germans were too weak to defend the river line effectively, and because the Allies had overwhelming air superiority.

But the figures for the Rhine are the exception, not the rule. At the Dnieper, in the autumn of 1943, the Soviet crossing of the river cost, by some estimates, hundreds of thousands of men, in one of the bloodiest operations of the war, because the Germans defended the far bank strongly and because the Soviet troops crossed in makeshift boats and on rafts, under fire, without proper equipment.

The figures for the Dnieper are disputed, and different sources give different totals, but the order of magnitude is not in dispute: the river crossing, when it is opposed, is one of the bloodiest operations in war.

The engineers’ war

The casualties of river crossings fall disproportionately on the combat engineers, the men who build the bridges and ferry the troops, and who work, unarmed and exposed, in the water and on the far bank. At the Rhine, the American engineers who built the pontoon bridges worked under German artillery fire, and they lost men to shelling and to drowning.

At the Berezina, the Dutch engineers who built the bridges worked in freezing water, and most of them died at their task. At the Dnieper, the Soviet engineers crossed first, in the assault boats, and they died in large numbers.

The engineers’ losses are rarely recorded separately — they are counted in the losses of the divisions they served — but they are, in every river crossing, among the heaviest, and they are a reminder that the river crossing is, above all, an engineer’s operation, and that the fate of the campaign depends, more often than not, on men with hammers and with pontoons, not on men with rifles.

8. Map and Geography

The river as a frontier

The geography of river crossings is the geography of Europe itself, because the rivers of Europe have been, for centuries, the frontiers of its states and the lines of its wars. The Rhine, which flows from the Alps to the North Sea, has been the frontier between France and Germany for more than 2,000 years, since the Romans made it the boundary of their empire, and it has been crossed, in war, more often than any other river in Europe: by Caesar, by Napoleon, by the Allies in 1945, and, in the other direction, by the Germans in 1940.

The Dnieper, which flows through Ukraine to the Black Sea, was the line on which the Soviet and German armies fought in 1943, and its crossing was the largest river crossing of the war on the Eastern Front. The Danube, which flows through central Europe to the Black Sea, was the line on which the Ottoman and Habsburg empires met, and it remains, today, the frontier of the European Union.

The map of Europe is, in large part, a map of its rivers, and the history of Europe is, in large part, a history of crossing them.

Choosing the crossing point

The choice of the crossing point is the most important decision in a river crossing, and it is a decision that depends on the map. The ideal crossing point is one where the river is narrow, where the banks are low and firm, where the far bank is not overlooked by high ground, and where the roads on the far bank lead to the army’s objectives.

The crossing point at Remagen was chosen by accident, because the bridge was there. The crossing point at Wesel was chosen by design, because the river was narrow there and because the ground on the far bank was flat and open. The crossing point at Oppenheim was chosen by Patton because it was unexpected: the Germans did not expect a crossing there, and they had not defended it.

In each case, the map determined the crossing, and the commander who read the map best crossed first. The river crossing is, in this sense, a test of the staff as much as of the troops: it tests whether the army has studied the ground, and whether it knows where the river can be crossed, and where it cannot.

9. Outcome and Legacy of River crossing

The crossing that ended a war

The Rhine crossing of March 1945 ended the war in the west, in the sense that, once the Allies were across the Rhine, there was no natural obstacle left between them and Berlin, and the German armies, which had been shattered in the west, could not stop them.

The crossing was the culmination of the Allied campaign in the west, which had begun with the landings in Normandy on D-Day, and it was the operation that made the victory possible. The legacy of the Rhine crossing is the legacy of the combat engineer: the pontoon bridge, the Bailey bridge and the assault boat, which were developed in the Second World War, are still the equipment of river crossings today, and the Bailey bridge, in particular, which was designed by the British engineer Donald Bailey in 1940, is still in use around the world, in war and in disaster relief, more than eighty years after it was invented.

The river crossing today

The river crossing is still studied, and still practised, today. The armies of the world maintain bridging regiments, and they train every year in river crossings, because the rivers have not gone away, and because the next war, like the last, will be fought across them.

In the war in Ukraine, which began in 2022, the rivers — above all the Dnieper — have again been the lines on which the war has been fought, and the crossing of the Dnieper, by both sides, has been among the most difficult operations of the war.

The destruction of the Kakhovka Dam in June 2023, which flooded the lower Dnieper, was a reminder that rivers are not only obstacles but weapons, and that the control of a river can decide a campaign. The river crossing, like the flanking manoeuvre and the counterattack, is a lesson that every generation of soldiers has to learn again, and it is a lesson that has not changed since Caesar crossed the Rubicon: the river must be crossed, and the army that can cross it will win.

10. Commanders

The engineers and the generals

Julius Caesar (Rome). The Roman general who crossed the Rubicon on 10 January 49 BC, and who, by that crossing, began the civil war that made him the master of Rome. Caesar was not only a general but a politician, and his crossing of the Rubicon was a political act as much as a military one. He went on to win the civil war, to become dictator of Rome, and to be assassinated on 15 March 44 BC. His account of his wars, the Commentaries, remains one of the great works of military literature.

Lieutenant Karl Timmermann (United States). The American officer who led the first men across the Ludendorff Bridge at Remagen on 7 March 1945. Timmermann, a lieutenant in the 9th Armored Division, ran across the bridge under fire, cut the demolition wires, and took the far bank. He was awarded the Distinguished Service Cross, and he died, of wounds, a few weeks later, on 30 March 1945. His exploit is still studied as an example of junior leadership in battle.

The commanders of the Rhine

Field Marshal Bernard Montgomery (Britain). The commander of the Twenty-first Army Group, who planned and executed Operation Plunder, the set-piece crossing of the Rhine at Wesel on 23 March 1945. Montgomery’s crossing was the largest and the most carefully prepared river crossing of the war, with a massive artillery bombardment, with assault boats, and with the airborne drop of Operation Varsity. It succeeded, and it was the last great set-piece battle of the war in the west.

General Omar Bradley (United States). The commander of the Twelfth Army Group, under whose command the Remagen bridgehead was exploited and the Rhine was crossed at Oppenheim. Bradley, who had commanded the First Army at Omaha Beach on D-Day, understood the river crossing as an operation of infantry and of engineers, and his exploitation of the Remagen bridgehead was one of the finest examples of seizing an opportunity in the war.

General George S. Patton (United States). The commander of the Third Army, who crossed the Rhine at Oppenheim on 22 March 1945, in a surprise crossing made without artillery preparation. Patton, who had boasted that he would cross the Rhine before Montgomery, did so, by a day, and his crossing was a model of speed and of surprise. He went on to advance across Germany to Czechoslovakia, and he died, in a car accident, in December 1945.

Frequently Asked Questions

What is a river crossing?
A military operation in which an army crosses a river in the face of enemy opposition, to establish a bridgehead on the far bank from which it can advance.

Why is a river crossing so difficult?
Because the crossing force is at its most vulnerable in the middle of the river, without tanks or artillery, while the defender holds the far bank with its guns registered on the crossing points and its reserves ready to counterattack the bridgehead.

What is a bridgehead?
A piece of ground on the far bank of a river, held by the crossing force, from which the main force can be passed across once the bridges are built. The bridgehead must be held against counterattack until the bridges are ready.

What happened at Remagen?
On 7 March 1945, American troops found the Ludendorff Bridge at Remagen still standing, because the German demolition charges had failed, and they crossed it under fire. The bridgehead was exploited, and within days five American divisions were across the Rhine.

What is a Bailey bridge?
A prefabricated, portable bridge designed by the British engineer Donald Bailey in 1940, which could be built quickly, by hand, under fire, and which is still in use around the world today.

What does “crossing the Rubicon” mean?
It means taking a decision from which there is no turning back. It comes from Julius Caesar’s crossing of the Rubicon on 10 January 49 BC, which began the Roman civil war.

Related articles

• Counterattack
• Flanking manoeuvre
• Unrestricted submarine warfare

Sources

1. Wikipedia, “River crossing” — the definition, the phases, and the classic examples.
2. Wikipedia, “Battle of Remagen” — the capture of the Ludendorff Bridge on 7 March 1945.
3. Wikipedia, “Operation Plunder” — the set-piece crossing of the Rhine at Wesel, 23 March 1945.
4. Wikipedia, “Operation Varsity” — the airborne drop behind the Rhine, 23 March 1945.
5. Suetonius, The Twelve Caesars — the account of Caesar’s crossing of the Rubicon.
6. Charles B. MacDonald, The Last Offensive (US Army Center of Military History, 1973) — the Rhine crossing and the end of the war in the west.

Further reading

• Ken Ford, The Rhine Crossings 1945 (Osprey, 2007) — Remagen, Plunder and Varsity.
• David M. Glantz, The Battle for the Dnieper, 1943 — the Soviet crossing of the Dnieper.