Warfare & Military Engineering
In Defense of Liberty
When besieged by ambitious tyrants I find a means of offence and defence in order to preserve the chief gift of nature, which is liberty.
— Leonardo da Vinci
Overview
Leonardo's military engineering was not a sideline — it was his primary credential when seeking patronage. His famous letter to Ludovico Sforza (c. 1482) lists military capabilities almost exclusively: portable bridges, siege engines, armored vehicles, cannons, tunnel-boring techniques. Only at the very end does he mention painting and sculpture.
The notebook material covers fortification design, weapons of every kind (from caltrops to bombards), pontoon bridges, siege tactics, and the devastating effects of artillery. There's a striking tension throughout: Leonardo was clearly fascinated by the engineering challenges of warfare, yet his epigraph — "to preserve the chief gift of nature, which is liberty" — suggests he saw military technology as fundamentally defensive.
He served as military engineer to Cesare Borgia in 1502 and later worked on fortifications for the Florentine Republic. The notebooks from these periods contain practical field observations alongside theoretical designs.
Practical Military Engineering
Pontoons, bridges, and field fortification
I can noiselessly construct to any prescribed point subterranean passages either straight or winding, passing if necessary underneath trenches or a river.
Since every river current is swifter in the centre of its breadth than at its sides, and flows faster on its surface than in its bed when the course is equal, and a movable bridge made upon barges is in itself weaker in the middle of its length than towards the extremities, therefore I conclude that as the greater weakness of the bridge is accompanied by the greater percussion of the water this bridge will break in the centre.
Make it so that in the movement of the bridge the length of the barges will always find itself in line with the current, when the movement will be so much easier as the barges receive less percussion from the water.
C.A. 176 r. c
Notice how Leonardo combines hydraulics, structural engineering, and practical field experience in a single observation. He doesn't just design a pontoon bridge — he analyzes why it fails and designs around the failure point. This is engineering thinking at its finest. -D
Weapons and Artillery
The terrible effects of bombardment
A way to make a cuirass: If you place between two thicknesses of cloth scales of iron and with this make a doublet you may take it as certain that no point will ever be able to penetrate.
C.A. 358 v. a
Again a bombard that takes a projectile weighing a hundred pounds is of considerably more use in the field than a small cannon, for that with pieces of rock inflicts considerable damage upon the enemy, and the small cannon or rather its ball, being of lead, does not rebound after the first blow by reason of its weight, and on this account it is less useful.
If you set an arrow so that it is just in equilibrium on top of a stone which seems on the point of falling over, you will perceive that a large bombard if discharged at a distance of ten miles from this arrow will cause such a tremor of the ground as to make the said arrow fall, or the stone upon which it is balanced.
C.A. 363 v. d
The Effects of Artillery
A vivid description of bombardment's destructive reach
Again if you discharge a small bombard in a courtyard surrounded by a convenient wall, any vessel that is there or any windows covered with cloth or linen will all be instantly broken; and even the roofs will be somewhat heaved up and start away from their supports, the walls and ground will shake as though there was a great earthquake, and the webs of the spiders will all fall down, and the small animals will perish, and every body which is near and which is possessed of air will suffer instant damage and some measure of loss.
But this small bombard should be discharged without its shell or if you so desire after the fashion of the curtail; and it will cause women to miscarry and also every animal that is with young, and the chicks will perish in their shells.
C.A. 363 v. d
"The webs of the spiders will all fall down, and the small animals will perish." Leonardo catalogs the collateral damage of artillery fire with the same observational precision he brings to water or light. The detail about spider webs collapsing from the shockwave is almost poetic. The detail about miscarriages is horrifying. He sees everything, and he writes it all down. -D
Field Tactics
Caltrops, night defense, and the movement of earth
If you are attacked by night in your quarters or if you fear to be, take care to have mangonels in readiness which can throw iron caltrops; and, if you should be attacked, hurl them in among the enemy and you will gain time to set your men in order against their assailants, the outwitted enemies, who because of the pain caused by the wounds in their feet, will be able to effect little. And the plan of your attack you will make thus: divide your men into two squadrons and so encircle the enemy; but see to it that you have soles to your shoes and that the horses are shod with iron, as I have said before, since the caltrops will make no distinction between your men and those of the enemy.
"The caltrops will make no distinction between your men and those of the enemy" — a perfectly Leonardo observation. He never forgets the second-order effects. Scatter caltrops and you stop the enemy, but you'd better have iron soles yourself. -D
Related Subjects
Source References
- MS. B — Major military designs
- MS. L — Borgia campaign field notes
There's an irony in Leonardo — the man who released caged birds for the pleasure of watching them fly — designing war machines. But this was Renaissance Italy. Every ruler needed engineers, and every engineer needed a ruler. Leonardo's military work bought him the freedom to pursue everything else. -D