One of the sillier questions military history buffs sometimes ask each other is how armies from different time periods would have fared in battle against each other. For instance, how would the Romans of Julius Caesar have dealt with the Norman heavy cavalry of William the Conquerer? Such questions are, it hardly needs to be said, fairly stupid and immensely fun. Today I’m going to take them seriously for a moment, but in doing so, I hope to illustrate why no one should ever take them seriously again. Along the way, we’ll learn a thing or two about military history. 

The big point people who conduct these thought experiments often arrive at is that up until the Early Modern period, perhaps the 16th century and later, the more historically recent armies don’t have a particular advantage over their earlier opponents. Dan Carlin, for example, in an episode of his Hardcore History, concluded that a fight between Romans and Normans would be too close to call, despite the thousand years of technological development between the two. 

Yet at the same time, military history is full of game-changing technological innovations. Look at the discovery of iron weapons, which revolutionized warfare in the near east, or the invention of the stirrup, which transformed the role of cavalry. From the very beginning, people have innovated and improved constantly. What’s more, military innovations seem somewhat more resilient than other sorts of technological changes. When ancient Rome fell, aqueducts and amphitheaters fell apart, but the armor and weapons used by Roman soldiers remained popular in much of Europe. 

This leads us to our central question. If military technology steadily improves over time, then how is it that more recent armies don’t wipe the floor with older armies? I believe there are two central reasons at play. 

Reason 1: Military systems shift constantly to respond to other military systems

Militaries have always designed their equipment, strategy, and organization to defeat other militaries of the same period. To achieve that goal, armies may use techniques which would be ineffective against the armies of earlier centuries.

Take the example of medieval European armor. For the early medieval period, most combatants wore mail, which is wonderfully effective at stopping bladed weapons. Over time, however, many soldiers began to use bludgeoning weapons like maces or morning-stars. To respond to the change, armorers developed plate mail. Plate mail was NOT a strict improvement over chain mail. Plate is heavier, more restrictive, and in some ways less effective than chain mail. But it was more effective against blunt attacks, and was therefore better for the purposes of medieval knights.

The constant rock, paper, scissors dynamic also appears in tactics. For much of pre-modern warfare, military logistics were so simplistic that guerrilla warfare was not an effective way to defeat large armies. However, in the 18th and 19th centuries, supply lines got longer and communication distances increased, so guerrilla warfare (one of the most technologically and logistically simple forms of warfare) made a big comeback. 

The bottom line is that any given military system is highly specialized at fighting its contemporaries, so much so that the most effective tactic against such an army is often to use tactics or equipment from an earlier date. The specialization of pre-modern armies largely nullifies any advantage an army from a later time might have on that from an earlier historical period. Speaking of “military capability” in the abstract sense isn’t nearly as useful as talking about “military capability against X”. 

Reason 2: Armies mirror the societies that produce them 

There is more to the picture than a military’s constant effort to improve itself. Contrary to what some say, the purpose of a military is not just to win wars. Militaries are designed to both reflect and maintain the society that produced them. In an attempt to increase social stability, states or other groups often make decisions that actually harm their ability to fight effectively. Unlike military technology, which gradually but consistently improves, societies during the pre-modern period did not become steadily more and more devoted to warfare. 

Warrior castes were an integral part of society and warfare for most societies in all of pre-modern history (and some parts of modern history, but that’s a story for another time). Knights and Samurai are the two most famous examples of warrior castes, but far from the only ones. Paradoxically, however, having a warrior caste can often impede the military ability of a society, since they have a tendency to resist reform and resent measures that improve the military effectiveness of the rest of the population. 

Social structures and norms have always been a far greater concern for humans than military victory. Just look at women in warfare. Throughout history, it has been vanishingly rare to recruit women to fight, despite the fact that women make up half of the population. True, most women have less manual strength than most men, but that does not explain why even in the most desperate circumstances, most societies have refused to use them in battle. To understand why, one must look to larger social concerns. Arming women would certainly upset the power structure of a male-dominated society. What’s more, women are far less expendable than men, since women are the limiting factor on population growth. 

Every society is different, forged by its geography, culture, and historical context. As a result, societies will limit their military arsenal in different ways. In 1139, Pope Innocent II banned Christians from using bows on other Christians (albeit with limited success). The society of ancient Carthage typically refused to recruit its own citizens for military service, preferring to rely on foreign mercenaries. The North American Plains Indians had a tradition called counting coup, wherein a warrior would try to touch enemy combatants with a stick as a display of courage. 

Warfare reflects a society’s economics, culture, and values. The overall performance of a society’s military, then, arguably has far more to do with politics and culture than military technology. Since political and social systems did not evolve at nearly so straightforward a way as military technology, it makes sense that some older societies might defeat newer ones in battle. 

The Bottom Line

In summary, pre-modern military systems did not gradually improve in all-round effectiveness because armies are a lot more complicated than just kitting out troops with the newest equipment and tactics. Warfare is not a universal condition, rather we might speak of many different types and philosophies of warfare, totally dependent on the cultural and military context in which they appeared.