The Rise of Steel Armor: From Romans to World War I
Explore how the Romans were the first to use steel in body armor and helmets.
The story of steel body armor begins with the Romans. They were the first to make use of steel in body armor, and were the first to use steel helmets in battle.  The steel armor and helmets of the Romans, which were frequently used alongside bronze pieces of similar design, were metallurgically sophisticated — wrought and then carburized, though not always quenched and tempered.
But to write the history of steel body armor from the Roman era would fill an entire book. The history of ballistic steel armor is a much shorter story.
We can begin by simply noting that the plate armor and helmets of the 14th-16th centuries were increasingly designed to withstand ballistic impacts, and, on that account, grew thick and heavy over time. Some of the helmets of that era weighed more than twenty pounds — and, though that’s an admittedly extreme example, and helmets that heavy were rare, helmets “of proof” – in other words, helmets rated to stop pistol shot and certain other of that era’s ballistic threats – never weighed less than five pounds.
Not surprisingly, steel body armor was also growing very thick and very heavy. In 1587, French military theorist and famed essayist Michel de Montaigne wrote:
“Today the officer is so heavily armed that by the time he becomes thirty-five his shoulders are completely humpbacked.”
In a separate account of roughly the same period, Montaigne also noted that:
“Alexander, the most adventurous captain that ever was, very seldom wore armour, and such amongst us as slight it, do not by that much harm to the main concern; for if we see some killed for want of it, there are few less whom the lumber of arms helps to destroy, either by being overburdened, crushed, and cramped with their weight, by a rude shock, or otherwise. For, in plain truth, to observe the weight and thickness of the armour we have now in use, it seems as if we only sought to defend ourselves, and are rather loaded than secured by it.”
In other words, the armor of the time was capable of saving lives, but nearly as many men died because of their armor — for it hindered their mobility, and prevented them from engaging in offensive operations, “as if we only sought to defend ourselves.”
Soldier and chronicler Pierre de Brantôme, a contemporary of Montaigne, likewise declared that men who wear heavy armor are “spent at thirty years.”
François de la Noue, a Huguenot captain known as “Iron Arm,” wrote much the same thing in Discours Politiques et Militaires, also published 1587:
“Our men of arms in the time of King Henry made a far fairer show … their armor wasn’t very heavy, so that they were well capable of wearing it for 24 hours. Those armors that are worn now are so weighty, that they will deaden a 35-year old Gentleman’s shoulders. I myself have seen the late Lord of Eguillie, and the knight of Puigreffier, honorable old men both, remain fully armed for a whole day, marching in the face of their companies — whereas now a young captain can hardly bear to remain fully armed and armored for two hours.”
The Musket’s Challenge to Armor
If armor was falling out of fashion in France and on the continent, things were much the same in England, and at much the same time. The English soldier, poet, and adventurer Sir Philip Sidney was shot in the thigh at the Battle of Zutphen in 1584, and, roughly a month thereafter, died of an infection caused by that wound. As Sir John Smythe describes it, Sidney’s death was because he wasn’t wearing all of his armor; just before the battle, he had noticed that one of his men was not fully armored, so he removed some of his own armor on the grounds that it would be dishonorable to be better armored than his troops.
Sidney’s death set off a heated controversy between English military experts of the era. De la Noue’s Discours was published in London, in English translation, in late 1587. In 1590, Smythe, a cousin of Edward VI and a lifelong soldier-of-fortune, wrote a small book on military practice titled Certain Discourses, wherein he came to the conclusion that armor is effective against every threat, except for the increasingly popular musket — “the blows of the bullets of which no armours wearable can resist.” In his book, he disparaged the musket and the arquebus for many reasons — noting, for instance, that they are slower to fire than the traditional English longbow, less accurate, and can be difficult to use in poor weather — but was unequivocal about their ability to pierce armor. As Smythe had it, the musket simply overmatched any armor wearable by man.
Sir Roger Williams and Humphrey Barwick both released books on the same topic later that same year, 1590. Williams, who like Smythe had seen a great deal of battle on the continent, disagreed with Smythe on many points — but not on the musket: “The best small shot that ever was invented.” Barwick, a war-hardened mercenary and adventurer like the others, was analytical about it, noting that:
“The musketes are weapons of great force, and at this day, bothe with leaders and followers, much feared: for fewe or no Armours, will or can defend the force thereof, being neerehand, which is as well a terror to the best armed, as to the meanest: it will kill the armed of proofe at ten score yardes, the common armours at twenty score, and the unarmed at thirty score, being well used in bullet and tried powder.”
Put another way, Barwick claimed that the musket can kill men wearing armor of “proof” — the very heavy steel body armor of the era which, generally, was built to stop firearm rounds — within 200 yards. Further, that it can kill men wearing “common armor” — mass-produced breastplates and helmets, called munitions-grade, generally much thinner and of poorer construction than armor of proof — at 400 yards. Lastly, that it can kill unarmored men at 600 yards. No surprise, then, that the musket was much feared, even by men wearing the heaviest armor.
All of the aforementioned experts lamented the fact that the armor and helmets of their era had become very thick, very heavy, and that its aesthetic qualities and its functionality both suffered for it — and that, nevertheless, men laden with even the heaviest armor of the era were still vulnerable to firearms. Plate armor reached its zenith — in functionality as well as in artistry — right around the year 1500, but it was already falling out of favor by 1580, thanks in large part to the development and increased utilization of the musket.
And indeed, just a few decades after this public debate raged across Europe, the Swedish attained great military victories in the Thirty Years’ War with very lightly armored and highly mobile musketeers and artillery. Although they didn’t invent the musket, they perfected its use — and they can stake a good claim to having invented mobile artillery with the famous leather cannon and the subsequent development of the light 3-pound gun, which could be pulled by two horses and operated by two men. As Gustav’s adversary Montecuccoli noted, and later emulated in battle, “one is appointed to load and fire, and the other conducts it by the end of the carriage, and brings it forward at the march tempo of the infantry.”
Gustav II Adolf and the Rise of Lightly Armored Forces
With respect to armor: Gustav II Adolf personally stopped wearing armor following a bullet wound to the shoulder sustained at the Battle of Dirschau in 1627. Ever since, he entered battle without armor — even to much larger battles than Dirschau, and to much greater victories. Gustav’s officers were naturally inclined to follow suit — either because they wanted to emulate their leader, because they felt that it would be shameful to be better-armored than Gustav himself, or merely to lighten their own burden.
In the ranks of Gustav’s infantry, pikemen were issued light steel helmets and heavier breastplates, but his musketeers and artillerymen — who outnumbered pikemen by at least two to one — were never issued steel body armor, and rarely wore helmets.
The cavalry situation was much the same. Cuirassiers were issued very light armor, if any at all, which would at most consist of a helmet and pistol-proof breastplate. They frequently wore no more armor than a buffcoat — a heavy leather jacket, as much as 5mm thick, that offered limited protection against slashing attacks, but exceedingly little against firearms or pike-thrusts. Gustav’s Dragoons — who were, practically speaking, a mounted infantry force — were not issued armor at all, and were armed in the manner of infantry musketeers. “They took us for musketeers, seeing that no animal in the world is more like a musketeer than is a dragoon, and if a dragoon falls from his horse, he rises up a musketeer.”
Gustav II Adolf’s lightly-armored force won decisive victories with speed and concentrated firepower, and battles like Breitenfeld (1631) marked a turning point in the history of warfare: For the first time, overwhelming firepower, in the form of muskets and light artillery, were utilized as the primary weapons of war. This presaged the era of maneuver warfare. Also, because it ushered in the demise of expensive steel armor, and because musketeers and gunners were fairly easy to recruit and train, these innovations also enabled, by 1670, a permanent increase in the size of standing armies. For these reasons, among others beyond the scope of this post, Gustav was rightly called “the father of modern warfare” by historians in the 19th century.
Thus by the late 16th century, soldiers were discarding their heavy “proof” armor and seasoned military experts were publicly deriding it. By the early 17th, the musket and light cannon attained battlefield supremacy, and breastplates and helmets, once considered essential, had ceased to be issued to most troops. Musketeers no longer wore helmets; they wore hats, often with very broad brims, as depicted more or less correctly in most of the art and sculpture inspired by Dumas’ Three Musketeers. But this doesn’t mean that armor vanished; there were more than a few holdouts — particularly in the heavy cuirassiers, who fought primarily with saber and pistol into the 19th century.
The Last Holdouts and 19th Century Cuirasses
The final cuirasses of those last cuirassiers – issued through the 19th century into the very early 20th – were of interesting construction: Unlike modern reproductions that are stamped from a sheet of homogeneous thickness, these cuirasses were between 5-6mm thick in their centers, and thinned out to roughly 2.3mm towards their edges. Generally, only the front-plate was of this construction; the back-plate was either much thinner, on the order of 1.2mm in maximal thickness, or was simply not worn. Such a front-plate could weigh more than 15 pounds, and at least some examples were known to stop the musket balls of the early 19th century at 40 yards. Beyond that, the metallurgical and performance characteristics of these 19th c. breastplates are largely unknown. It’s plausible that those made before roughly 1880 were made of puddled iron, and thus it’s highly likely that they contained very little carbon and were of relatively low strength and hardness. Those made after 1880 may have been made of Bessemer steel; these may have been unquenched and ferritic/pearlitic, and thus also of relatively low strength – but we can only guess, for a late-19th century cuirass has never before been subjected to a modern metallurgical analysis. In any case, such breastplates were worn by the French cuirassiers in the first weeks of WWI, but it was found that they offered exceedingly poor protection from small arms, and they were quickly dropped.
So it was that at the outset of World War One, the overwhelming majority of soldiers were issued no protective armor of any kind – and the few that were issued breastplates discarded them within weeks of entering the war.
This comprehensive journey through the history of steel body armor showcases how warfare, technology, and strategy have shaped the evolution and eventual decline of this once-vital protective gear.
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