Giant crossbow

A letter from the west coast of India addressed to the Florentine regent Giuliano de’ Medici in 1515 is revealing. A seafarer named Andrea Corsali reported that he had discovered gentle people clad in long robes who lived on milk and rice, refused any food that contained blood, and would not harm any living creature—“just like our Leonardo da Vinci.” Corsali was describing the Jains, known for their extreme nonviolence; in the twentieth century they would have a profound influence on Mahatma Gandhi.

One of Vasari’s loveliest anecdotes about Leonardo concerns the artist’s love of animals: “Often when he was walking past the places where birds were sold, he would pay the price asked, take them from their cages, and let them fly off into the air, giving them back their lost freedom.” Did Leonardo, who had an exceptional desire for freedom and himself tried to fly, feel a special rapport with birds?

Of course Corsali would not have been reminded of the artist far away if Leonardo’s attitude had not seemed so remarkable. That a person would display empathy at all was quite unusual in this era, which had been devastated by violence. But the idea of actually forswearing the consumption of meat out of simple consideration for other creatures was unheard of in the West.

Vasari, who later wrote a biography of Leonardo, may have known these and other reports about customs in the Orient. In the Buddhist countries of Southeast Asia birds are offered for sale in front of some temples even today so that people who want to ensure good karma can buy their freedom and send them soaring into the air. Vasari’s account of Leonardo’s bird liberation may have been no more than an appealing embellishment to his text.

Still, there is no doubt that Leonardo had a deep-seated aversion to all violence, as several passages in his notebooks confirm. His attitude certainly had more in common with the ethos of Eastern nonviolence than with the harsh customs then prevalent in the Christian West. Precisely because he respected the value of every creature, he was firmly convinced of the sanctity of human life. In reference to his anatomical studies, he wrote: “And thou, man, who by these my labours dost look upon the marvelous works of nature, if thou judgest it to be an atrocious act to destroy the same, reflect that it is an infinitely atrocious act to take away the life of man.”

Scythed chariot

Leonardo’s words make it difficult to grasp the gruesome fantasies his mind was capable of in designing his engines of war. On hundreds of pages, Leonardo sketched giant crossbows, automatic rifles, and equipment to bombard strongholds with maximal destructiveness. The sole function of these devices was to kill and destroy. He did not just record the technology, but provided graphic descriptions of the devastating impact of his inventions. In one sketch, archers are running away from an exploding grenade, which Leonardo referred to as “the deadliest of all machines.”4 In another, a war chariot with rotating scythes as large as men is mowing down soldiers and leaving behind a trail of severed legs and dismembered bodies.5 The battle plans Leonardo drew up are equally chilling. On Sheet 69 of Manuscript B, housed in Paris, we read about his preparations for chemical warfare:

Chalk, fine sulphide of arsenic, and powdered verdigris may be thrown among the enemy ships by means of small mangonels. And all those who, as they breathe, inhale the said powder with their breath will become asphyxiated. But take care to have the wind so that it does not blow the powder back upon you, or to have your nose and mouth covered over with a fine cloth dipped in water so that the powder may not enter.6

His involvement in the wars of his era extended well beyond the design of weapons and began even before he signed on with the in – famous, bloodthirsty Cesare Borgia in 1502. How could a man whose sense of empathy is said to have inspired him to free birds from their cages come up with ideas of this sort?

On one occasion, Leonardo justified his military activities with a statement that a modern-day reader could easily picture coming straight from the Pentagon: “When besieged by ambitious tyrants, I find a means of offense and defense in order to preserve the chief gift of nature, which is liberty.”

Doubts are certainly warranted here; after all, his first employer, Ludovico Sforza, was not exactly a champion of freedom. The historian Paolo Giovio, a contemporary of il Moro, called him “a man born for the ruin of Italy.” That might sound harsh, but without a doubt, “the Moor” was a major reason that Italy lost its freedom for centuries and became a battlefield for foreign powers.

Ludovico, an inveterate risk-taker, sized up his position on his very first day in power and realized that he was surrounded by enemies. In his own empire his right to rule was in dispute, since he owed his power to the violent murder of his brother, for which no one had been charged, and the arrest of the sister-in-law. Moreover, Venice and the Vatican tried to exploit Ludovico’s insecure position, and they armed for war. In March 1482, the Venetians attacked Ferrara, which was an ally of il Moro. At this time, Leonardo arrived in Milan and in his famous ten-point letter of application promised il Moro a whole new arsenal of weapons. Two years later, Ludovico was able to defeat the Venetians.

But il Moro, who was focusing all his efforts on legitimating his rule once and for all, needed a seemingly endless supply of weapons. Over the next few years, his dodges would determine not only the further course of Leonardo’s unsettled life but also result in the so-called Italian Wars, which lasted sixty-five years and brought about the political collapse of the country.

The disaster ran its course when Ludovico sought a strong ally against Naples. The king of Naples, Ferdinand I, had meanwhile given his daughter’s hand in marriage to the legitimate heir to the throne in Milan, Gian Galeazzo, and was quite indignant when he realized that Ludovico had no intention of ceding power to his son-in-law. Ludovico encouraged Charles VIII of France to invade Italy to overthrow Ferdinand. What followed was a bloody farce: Charles was asked to invade Lombardy with forty thousand soldiers, whereupon Gian Galeazzo was murdered. Two days later, Charles declared il Moro the legitimate duke of Milan. But the latter showed no gratitude. When the Neapolitans rebelled against the French occupation in the following year, the opportunist switched sides and entered into an alliance with Venice and the pope. The French were expelled and suffered great losses.

Just a few decades earlier, wars had been highly ritualized battles with relatively few casualties, but now they were developing into horrific bloodbaths. The handgun had been widely adopted; a few years later, Leonardo would contribute a wheel lock, which was one of the handgun’s first effective firing mechanisms. And there were growing numbers of portable cannons on battlefields. Since the earlier stone balls had been replaced by metal projectiles, the firearms shot more effectively than ever before, as Charles VIII’s soldiers proved when they demolished the ramparts of the mighty castle of Monte San Giovanni Campano with small cannons within hours, before attacking Naples. Until then the battle was won by the side that had more and better soldiers. From this point on, technology was key.

Leonardo had promised marvelous weapons to il Moro and was granted a tremendous degree of freedom in return. As the engineer of the duke, he received a fixed salary and no longer had to rely on selling his art on the market. This was the only way he could pursue his research interests and continue to perfect his paintings without any pressure to meet deadlines. We owe the magnificence of the Milan Last Supper, the studies of water, and his explorations of the human body to Leonardo’s clever move of offering himself up to one of the most unscrupulous warlords of his era. During his first seventeen years in Milan, serving Ludovico, he sketched the great majority of his weapons, among them his most dreadful ones.

All the same, Leonardo’s interest in weapons went far beyond the steady job they brought him. His drawings reveal an unmistakable fascination with technology. In the end, his inventions were the product of his inexhaustible fantasy, which gave rise to paintings, stories, projects to transform entire regions, tools—and weapons. One of these weapons, which he designed in Milan, looks like a water mill, but is actually a gigantic automatic revolver. Leonardo arranged four crossbows in a compass formation, with one pointing upward, one downward, one to the left, and one to the right. The wheel was powered by four men running along its exterior to turn it at breakneck speed. An ingenious mechanism with winches and ropes caused the bows to tighten automatically with each turn. The marksman crouched in the middle of the mechanism and activated the release. In one version, the wheel was equipped with sixteen rather than four crossbows. Leonardo devoted himself to refining the driving mechanism as well.

Even so, in comparison with the truly revolutionary firearms of the era, this contraption looks charmingly old-fashioned. At least for the years until 1500, Kenneth Clark was probably right in claiming that Leonardo’s knowledge of military matters was not ahead of his time. Even Leonardo’s most spectacular weapon, the giant crossbow he invented in 1485, was not really pioneering. With a 98-foot bow span, this monster was intended to stand up to cannons, to fire more accurately, and to save the soldiers from often fatal accidents with exploding gunpowder. There is no evidence, however, that anyone attempted to construct this giant crossbow during Leonardo’s lifetime. More than five hundred years later, when a British television production undertook this project, the results were pitiful. Specialized technicians were brought in to build a functionally efficient weapon using twentieth-century tools, guided by Paolo Galluzzi, one of the leading experts on Renaissance engineering. Since they were required to restrict their materials to those that were available in the Renaissance, they opted to build a bow with blades made of walnut and ash that would be five times larger than any before. A worm drive designed by Leonardo himself had to muster a force equivalent to the weight of ten tons to tighten this enormous spring, thus making it possible to catapult a stone ball over 650 feet. But when British artillerymen tried out the construction on one of their military training areas, the balls barely left the weapon. After a mere 16 feet in the air, they plopped to the ground. Video recordings showed that they could not detach properly from the bowstring. When the technicians added a stopping device to the string (not drawn by Leonardo), the range increased to 65 feet— still hardly sufficient to produce anything but guffaws on a Renaissance battlefield. And the fact that the replicators had made the bow thinner than in Leonardo’s design came back to haunt them—the wood broke.

When you look at many of Leonardo’s drawings from his years in Milan, it is hard to shake the feeling that Leonardo had no intention of supplying serviceable weapons. It seems to have been far more important to him to impress his patron—especially when he emphasized the enormous dimensions and the impact of his weapons. As the most talented draftsman of his generation, he knew how to create a dazzling effect. Leonardo enjoyed an outstanding reputation as a technician of war because he was a great artist. He portrayed the details of his designs so meticulously, using the effects of perspective, light, and shadow so skillfully, that it was easy to mistake reality for wish. The drawing of the giant crossbow features not only the knot of the string and the details of the trigger mechanism, but also the soldier handling the weapon. Like the face on the Mona Lisa, Leonardo’s war machines seem alive.


While Leonardo proved a master of illusion in designing weapons, he also made concrete contributions to military development. Military commanders needed to figure out how to put the latest firearms—mobile cannons—into action. How should they shoot? With bows and crossbows, the shooter simply aimed straight ahead; the range of the new firearms, by contrast, meant that the trajectory curve had to be determined to make the cannonball hit its target. But no one had a clear idea about the laws governing the paths of cannonballs. Progress on this matter could determine the outcomes of wars.

Traditional physics offered little help, because this discipline still adhered to the ancient view that a body moves only while a force acts on it. But if that were so, a cannonball would come to a standstill just after leaving the barrel of the cannon. The seemingly plausible concept of “impetus” was introduced: The cannon gives the ball its impetus, and only when the impetus is completely used up as it flies through the air does it fall to the ground. The cannoneers of the time were well aware that the impetus theory could not be correct; anyone who relied on it was off the mark. The error is that gravity sets in immediately to begin pulling down on the cannonball.

Leonardo’s interest in this question went far beyond its military implications. He was determined to figure out the laws of motion. He kept going around in circles because he could not relinquish the idea of impetus and because the crucial concept of the earth’s gravity was still unknown at the time. His notebooks document how bedeviled he was by the laws of motion. His explanations of mechanics were riddled with inconsistencies; at times he argued both for and against impetus within the space of a single paragraph.

But then he had a brilliant idea of how to determine the trajectory of projectiles not by conceptualizing, but by observing: “Test in order to make a rule of these motions. You must make it with a leather bag full of water with many small pipes of the same inside diameter, disposed on one line.” One sketch shows the small pipes in the bag pointing upward at various angles, like cannons that aim higher at some points and more level at others. The arcs formed by the spurting water correspond to the trajectories of the cannonballs. Leonardo’s trajectories were accurate in both this sketch and others. By means of a clever experiment—not involving mathematics—he had discovered the ballistic trajectory that Isaac Newton finally worked out mathematically some two hundred years later.

This little sketch offers a glimpse inside Leonardo’s mind. He was able to link together fields of knowledge that appeared utterly unrelated. From the laws of hydraulics, which he had investigated so exhaustively, he gained insights into ballistics. His thoughts ran counter to the conventional means of solving problems. Instead of attacking the matter head on, formulating the question neatly, and penetrating more and more deeply below the surface, Leonardo approached the problem obliquely—like a cat burglar who has climbed up one building and from there breaks into another across the balconies. Leonardo was unsurpassed in what is sometimes called “lateral thinking,” which enabled him to explain the sound waves in the air by way of waves in the water, the statics of a skeleton by those of a construction crane, and the lens of the eye by means of a submerged glass ball.

Leonardo’s experiments with models also represented a new approach. Since he neither understood how to use a cannon nor was able to observe the trajectory of an actual cannonball up close, he used a bag filled with water as a substitute. Of course an approach of that sort is unlikely to yield a coherent theoretical construct, because similarities between different problems are always limited to individual points, and Leonardo was far too restless to pursue every last detail of a question. Still, his models yielded astonishing insights. The French art historian Daniel Arasse has aptly called him a “thinker without a system of thought.”

In an impressive ink drawing, Leonardo illustrated the damage that could be inflicted by applying his insights into ballistics. A large sheet in the possession of the Queen of England shows four mortars in front of a fortification wall firing off a virtual storm of projectiles. Not a single square foot of the besieged position is spared from the hundreds of projectiles whizzing through the air. For each individual one, Leonardo marked the precise parabolic trajectory, and the lines of fire fan out into curves like fountains. Ever the aesthete, Leonardo found elegance even in total destruction.

Saturation bombing of a castle

It is difficult to establish to what extent Leonardo’s knowledge of artillery was implemented on an actual battlefield. When Ludovico had Novara bombarded in February 1500, the mortars were so cleverly positioned that the northern Italian city quickly fell. In the opinion of the British expert Kenneth Keele, il Moro was using Leonardo’s plans for a systematic saturation bombing.

Leonardo’s close ties to the tyrants of his day offer a case study of the early symbiosis of science and the military. Now as then, war not only provides steady jobs and money to pursue scholarly interests, but also prompts interesting theoretical questions. Even a man as principled as Leonardo was unable to resist temptations of this sort. He was not the first pioneer of modern science and technology to employ his knowledge for destructive aims. Half a century earlier, Filippo Brunelleschi, the inspired builder of the dome of the Florence Cathedral, had diverted the Serchio River with dams to inundate the enemy city of Lucca. (This operation came to a disastrous end; instead of putting Lucca under water, the Serchio River flooded the Florentine camp.) Leonardo’s struggle to strike a balance between conscience, personal gain, and intellectual fascination seems remarkably modern, and brings to mind the physicists in Los Alamos who devoted themselves heart and soul to nuclear research until the atomic bomb was dropped on Hiroshima.

Of course we cannot measure Leonardo’s values by today’s standards. We have come to consider peace among the world’s major powers a normal state of affairs now that more than six decades have passed since the end of World War II, but we need to bear in mind that there has never been such a sustained phase of freedom from strife since the fall of the Roman Empire. In Italy, the Renaissance was one of the bloodiest epochs. The influence of the Holy Roman Empire had broken down, mercenary leaders had wrested power from royal dynasties, and a desire for conquest seemed natural. War was the norm, and a prolonged period of peace inconceivable.

Leonardo’s refusal to regard death and destruction as inescapable realities is a testament to his intellectual independence from his era. As far back as 1490 he was calling war a “most bestial madness.” And one of his last notebooks even contains a statement about research ethics. While describing a “method of remaining under water for as long a time as I can remain without food,” he chose to withhold the details of his invention (a submarine?), fearing “the evil nature of men who would practice assassinations at the bottom of the seas by breaking the ships in their lowest parts and sinking them together with the crew who are in them.” The only specifics he revealed involved a harmless diver’s suit in which the mouth of a tube above the surface of the water, buoyed by wineskins or pieces of cork, allows the diver to breathe while remaining out of sight.

Leonardo must have had his reasons for withholding particulars about the dangerous underwater vehicle. Perhaps his ideas were still quite vague, or he was afraid that imitators might thwart his chances for a promising business. But the key passage here is Leonardo’s statement about the responsibility of a scientist. He was the first to assert that researchers have to assume responsibility for the harm others cause in using their discoveries. Insights like these, and his high regard for each and every life, were quite extraordinary at the time. It is amazing that he embraced these ethical principles—but not surprising that he repeatedly failed to live up to them, at least by today’s standards.


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