EMPIRES OF IRON AND STEEL
The finest Steel blades of Rome, discovered in Scandinavia?
Published on 30 Aug, 2021
Introduction
Iron is a cheap and abundant material in the modern world, but if we rewind time for 3,500 years, Iron's value was completely different. In the Bronze Age world, Iron used to be a precious metal more valuable than Gold. Once upon a time, Iron signified wealth and power.
Why?
The explanation is rather simple, back in the Bronze Age, Iron came from meteors from the heavens almost exclusively. "Meteoritic Iron" was rare, and people craved for them just like other precious metals and gems. Iron was used to make jewelry, examples have been discovered by archaeologists working on Bronze Age Aegean sites, including the famous Mycenae itself.
The invention of Iron smelting in Anatolia and its spread to the entire Near East
The precise timeline of the invention of Iron smelting is still pretty much a mystery. What we know is: it most probably originated from Central Anatolia in modern-day Turkey. Sample recovered from the Hattian site of Kaman-Kalehöyük is the first archaeological evidence of Iron extraction from ore in human history. Further analysis also showed that the Iron was carburized into steel, an alloy of Iron and Carbon which is much harder than pure Iron. When the Indo-European Nesite people came and built the Hittite Empire, they inherited the Iron-making technology from the native Hatti people and quickly became an important producer and exporter of this valuable material in the Eastern Mediterranean.
A famous document called "Letter from Ḫattušilis III of Hatti to Adad-nārārī I of Assyria" is a vivid demonstration of the value of Iron for Ḫattuša as a diplomatic gift. In this world-famous document, Iron for diplomatic gift was referred to as "good Iron" (AN.BAR SIG5), and hence we know that the Hittite Empire was producing two different types of Iron, one of them had better quality than the other. Hittite documents also mentioned that international treaties were inscribed on metal tablets including Gold, Silver, Bronze and Iron.
In regard to the good iron (AN.BAR SIG5 ) about which you wrote to me - good iron is not available in my memory in the city of Kizzuwanta. I have written that it is a bad time for making iron. They will make good iron, but they have not yet finished it. When they finish it, I will send it to you. For the moment I have sent you a dagger blade of iron.
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Historians traditionally believed that the Hittite Government regarded the production method of Iron a closely guarded state secret, and Iron was only produced in state-owned workshops specializing in this purpose. This view has become more controversial in recent years, and at present, there is a growing academic consensus that Iron-working was not exclusive to the Hittites. Nevertheless, the diffusion of Iron metallurgy was centered in Anatolia and rapidly spread outward after the collapse of the Hittite Empire in early 12 Century BCE. Excavation in the Caucasus region showed that pre-Urartian Van region (Nairi in Assyrian record) quickly entered the Iron Age, and Iron artifacts turned up in large quantity in archaeological sites not long after the collapse of Hittite Empire. Since it is generally assumed that the Van region united into a monarchy sometime in 10 Century BCE, therefore, Van region's transition from Bronze Age to Iron Age must predate the the rise of the Urartian Kingdom. Contrary to the Van region, sites in modern Armenia yielded much less Iron artifacts at the same time. This is consistent with the hypothesis of Anatolia-to-Caucasus gradual diffusion of Iron-working technology.
In the following Centuries, Iron weapons gradually displaced Bronze in the Near East and Levant, though body armors remained Bronze for much longer, due to the obvious reason that Bronze was much easier to work with than Iron. During the reign of Neo-Assyrian King Sargon II (721-705 BCE), the Assyrian Army gradually replaced Bronze weapons with Iron and Steel. Urartian spears from the same period were already made of high-Carbon Steel with a Carbon content of up to 0.6%. The 7 Century BCE Vered Jericho Sword, now on display in The Israel Museum, Jerusalem was also made of crucible steel and reached a length of 105cm. Remarkable!
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Rome: an Empire of Iron and Steel
Since the collapse of the Hittite Empire, Iron gradually replaced Bronze as the first choice of material for swords, daggers, and body armors in Western Eurasia. However, it was not until the Romans when ferrous metallurgy reached an apex in both quantity and quality.
It is generally believed that Rome was one of the top pre-industrial Iron producers, and an undisputed number 1 in Classical time, judging from the widespread civilian and military use of Iron. Discoveries in Pompeii and Trajan's Column showed that Romans protected their cart wheels with a ring of Iron, in both military and civilian vehicles. This is a vivid proof of the abundance of this material in the Empire. Iron was also used in construction of monumental buildings in Rome. Wooden bridges and trusses were found to be reinforced with Iron parts, and Iron clamps were used to fix marble panels to concrete buildings to give them an elegant appearance. One prime example is the Flavian Amphitheater, or the Colosseum in Rome. The Colosseum once had 200-300 tons of Iron clamps for this purpose.
The Flavian Amphitheater (the Colosseum)
The large number of holes on the Colosseum building were once attachment points for decorative marble panels. After the Iron clamps and marble panels were removed and recycled, the holes were exposed to the outside and became visible.
In order to supply enough Iron and Steel to satisfy the need of the vast Empire, the scale of Iron production in Roman territory was nothing short of spectacular. Iron slag disposal sites were discovered all over Europe, they are called ferriers. The Romans produced Iron on an almost industrial scale and left countless mounds of slag, which is the waste product of Iron smelting. In the ferrier of Tannerre-en-Puisaye, France, 30ha of landscape was littered with Iron slag mounds, and 80% were deposited during the 300 years of Roman operation. Another major ferrier in France is Les Martys, both are among the largest in Europe. In modern Serbia, the ferrier of Majdanpek is 6+ ha in area and slag heaps were 2-7m high. in some parts of the Empire, bituminous coal was utilized for the smelting of Iron, and in the Alps, even high altitude mines were exploited during Roman time.
So, how much Iron did Rome produce each year at its height? An estimated annual output of 80,000 tons would make Rome an uncontested global top Iron producer for a millennium. It is possible that Northern Song Dynasty of China reached a comparable annual Iron output, or even surpassed the Roman level in its Golden Age from 960 CE to 1,126 CE, according to Robert Hartwell's estimate in 1962. His high estimate of 75,000 to 150,000 tons per year for Song, like the number for the Romans, is a guesstimate at best and is not without controversies. Under any circumstances, the abundance of Iron and Steel in ancient Rome, and the near-industrial scale of production, is exceedingly rare in the ancient world.
The treasures of Nydam
Contrary to a popular belief that Rome did not produce fine steel weapons and imported most of its high quality steel from the East, Rome was indeed capable of making some of the finest swords at its time. Analysis on some Roman Gladius belonging to Mainz and Fulham types revealed that their blades were quench-hardened high Carbon steel with an edge hardness of up to 770HV. Noric steel, originating from the Roman province of Noricum in the Danube frontier region, also earnt the reputation of being some of the finest steel production region in the Empire. However, ironically, it is not inside Roman territory where the finest examples of Roman steel was discovered.
Roman long swords (Spatha) discovered in the Nydam bog, Denmark were not just the best Roman swords discovered, but some of the finest in the entire ancient world. They are collectively called "The Nydam Swords". Metallographic analysis shows that the blades were properly carburized to high Carbon Steel with 0.9% Carbon content, they were quenched and heat-treated, with an edge well-hardened to a value up to 937HV and the core hardness remained low at just 260HV to maintain flexibility. The lower Carbon content and the absence of Martensite at the core explains its softness. Maintaining the softness at the core is critical for achieving the desirable mechanical properties, because if the entire blade was hard across the section, then the sword would become brittle. Multiple examples of steel swords with a blade edge hardness in excess of 900HV were discovered, even though not all Nydam swords reached this level of hardness.
Fine Roman steel swords discovered in Nydam bog, Denmark
Apart from offensive weapons, Roman armors also utilized Iron and Steel. Lorica segmentata were designed to be mass-produced as a standardized body armor for the Legionaries. A medium-carbon steel exterior layer protected the soldier from the penetration of arrowheads and swords, while the interior layer of soft Iron maintained the curvature necessary to fit the shape of the human body.
Despite Pliny's praise of imported Indian steel, which is also a fact, Rome indeed produced it own high quality steel competitive globally in terms of mechanical properties for use as weapons and armors.
The Nydam boat discovered in Sønderborg, Denmark
How Roman swords ended up in Scandinavia?
One last concluding remark: how did such a huge collection of fine Roman swords ended up in Denmark, which has never been under Roman rule? Since Roman Law prohibited the export of strategic resources to Germanic tribes, we end up with two possibilities: illegal trade and war trophy. Nowadays, it is generally believed that the Nydam swords were recovered by the Danes from defeated Romans, and the Scandinavian tradition of sacrificing the swords by bending them and throwing them into lakes, which happen to be alkaline in nature and prevented the corrosion of metals, helped preserved them to the the present days.
References and footnotes
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Bryce T. (2005) The Kingdom of the Hittites, Ch. 2, pp. 30, Appendix 2 pp. 383. Oxford University Press. Oxford, UK.
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Beckman G. (1999) Hittite Diplomatic Texts, 2nd Edition, II.24B "Letter from Hattusili III of Hatti to Adad-nirari I of Assyria", pp.148. ScholarsvPress. Atlanta, USA.
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Fuchs A. (2017) A Companian to Assyria, Ch. 11, pp.250-253. WILEY Blackwell. Chichester, UK.
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Çifçi A. (2017) The Socio-Economic Organisation of the Urartian Kingdom, Ch. 2.3.4.1, pp. 132-139. Koninklijke Brill. Leiden, The Netherlands.
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http://leferrierdetannerre.net/index.php/fr/ferrier/historique/periode-gauloise
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Morin D., Rosenthal P., Fontugne M. (2007) Roman-early medieval iron mining and smelting at high altitude in the Alps (Argentera-Mercantour massif - Alpes-Maritimes, France). Antiquity 81(313), Antiquity Publications/Cambridge University Press. https://hal.archives-ouvertes.fr/hal-00376449
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Hartwell R. (1962) A Revolution in the Chinese Iron and Coal Industries During the Northern Sung, 960-1126 A.D. The Journal of Asian Studies Vol. 21, No. 2 (Feb., 1962), pp. 153-162.
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Craddock P. T. (2008) The Oxford Handbook of Engineering and Technology in the Classical World, Ch. 4, pp.108. Oxford University Press. New York, USA.
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Lang J. (1988) Study of the Metallography of some Roman Swords. Britannia 19, pp. 199-216. https://doi.org/10.2307/526199
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Buchwald V. F. (2005) Iron and Steel in Ancient Tmes, 1st Edition, Ch. 11, pp. 264-291. The Royal Danish Academy of Sciences and Letters. Copenhagen, Denmark.
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Fulford M., Sim D., Doig A. and Painter J. (2005) In defence of Rome: a metallographic investigation of Roman ferrous armour from Northern Britain. Journal of Archaeological Science 32 (2). pp. 241-250. Elsevier. Amsterdam, Netherlands.https://doi.org/10.1016/j.jas.2004.09.003