What the Fall of the Roman Empire Has Taught Me About Military Expansionism

It began with a series of small scale wars between Rome and its Italian neighbors, the Latins, the Sabines, the Umbrians, and others. The Etruscans were the first to fall. The Etruscans had been the dominant power in the Italian peninsula for 150 years, but in 500 BC the small city-state of Rome revolted and gained its independence, rejecting the monarchial form of governance imposed on it by the Etruscans and adopting something new, a republic.

Latium and the Italian Peninsula

The weakening of the Etruscans enticed the Sabines to try to take over. The Romans went to war with them in 493 BC and won. Then the Romans defeated the Volsci, the Aequi, and the Veii. By 390 BC Rome was the dominant power in Latium, the region of western Italy where the city of Rome is located.

From there Rome pushed south into the Italian peninsula, defeating the Samnites and throwing out the Greeks. By 270 BC Rome controlled the peninsula. Then they turned their sites on Sicily.

At the time Sicily was ruled by the Carthaginians, a rival superpower based in North Africa. While Rome had been expanding through the Italian peninsula, the Carthaginians had been expanding around the Mediterranean, laying claim to Spain, the north African coast, and Sicily. Sooner or later it was inevitable the two powers would come to blows.

Rome Takes Over the World

Over the course of 120 years and three harrowing conflicts, the Romans and Carthaginians fought. These were the Punic Wars, and the eventual outcome was decided in Rome’s favor. In 146 BC Carthage and North Africa were taken over by the Romans, along with Spain and Sicily. Now Rome was an international superpower, but the momentum it gained in expanding so rapidly could not be reined in. Military expansionism was now its raison d'être.

In the first century BC Rome seized territory in modern day Turkey and the Levant, taking possession of Judea in 63 BC. Between 58 and 50 BC Julius Caesar waged war against the Gauls in modern day France.

In 52 BC the Gauls were toppled, then Julius Caesar marched on Rome and tried to establish a dictatorship with himself at its head. Ceasar was assassinated, but his nephew Augustus rose to power and became Rome’s first emperor. Augustus ruled over an enormous Empire. By the first century AD the Roman Empire had expanded as far north as modern day Belgium and as far east as Syria. The Roman military was a well-oiled machine without rival. It could impose its will wherever it wanted, but it would only remain in good order if it kept pushing.

The Danger of Stopping Short

This is the problem with military expansionism. It only works when it’s working. Like a bulldozer building a levee against a rising flood, it must keep going, for the minute it falters or takes a break it will be overwhelmed. However, this analogy falls short of describing the source of that flood. Tragically and ironically, the flood is created by the aggressor itself. An expansionist power like Rome frightens and antagonizes those who oppose it. If the opposition fails, they are subjugated, but if they succeed in evading the aggressor, they grow more powerful, a greater and greater threat. The aggressor nation cannot rest. It must keep pursuing all its enemies. In time this grows exhausting.

Consider the Nazis. From 1936 to 1939 the Nazis won a string of victories, taking territory after territory unchallenged. In 1939 the allies finally decided to fight back, but by then the military expansionism of the Nazi’s was a well-oiled machine. They kept pushing. The Netherlands fell, Belgium, and then France. Hitler was ready to take a break. He stopped short of invading Great Britain. He thought the British could be brought around at the negotiating table. This was a fatal mistake. How differently things might have been if the Nazis had taken Great Britain.

In due course, and with the help of the United States, the British fought back, while on the eastern front, the Soviets turned the tide and drove the Nazis from their soil. Suddenly the aggressors were on the defensive. The hunters became the hunted. The Nazi superpower collapsed like a house of cards. From the Nazi defeat at the Siege of Stalingrad in February 1943 to Germany’s surrender in April 1945 only fourteen months elapsed. The Nazi juggernaut was completely eradicated. This is the danger of stopping short.

The Beginning of the End 

The Romans too stopped short. In 122 AD the Roman Emperor Hadrian was troubled by unrest in various parts of the Empire. Uprisings in Judea and North Africa were a thorn in his side, and then there were the Picts, a tribal people from modern day Scotland. The Picts had attacked Roman forts along the frontier in Roman Britannia, more than 1,400 miles from Rome itself. To Hadrian this seemed like an impossibly long way away to prosecute a war, especially with Rome under so many other threats closer to home. So, rather than attack, Hadrian built a wall and hoped it would be enough. It wasn’t.

Less than eighteen years after it was built, Hadrian’s Wall was deemed inadequate. Hadrian’s successor Emperor Antoninus Pius built a second wall farther to the north. It too failed to keep the Picts at bay. For the next 200 years the Romans struggled to keep the Picts and other northern tribes from attacking across the border into Roman territory. Finally, in 410 AD they gave up altogether and withdrew from Britannia.

By then Roman power was collapsing across the Empire. Hadrian’s hesitancy had cost Rome. Not only had Hadrian stopped short in Britannia, he had also ordered the withdrawal of troops from western Dacia (modern day Romania and Ukraine). It was Hadrian’s intention to reverse the aggressive militarism of his predecessors, opting instead to secure and consolidate existing territories. Hadrian was an astute administrator, but no amount of sound administration can appease the anger of those who have been suppressed for too long. The flood topped the levee. Rome was overwhelmed.

The Lesson Learned

The barbarian invasions of the fifth century were a direct result of Rome’s change in policy. Germanic tribes who had long been on the defensive were suddenly on the offensive. Province after province fell. In 476 AD the Western Roman Empire ceased to exist altogether, completely overwhelmed by barbarian tribes.

This is the lesson of Rome's experience: Countries that engage in military expansionism inevitably come to ruin. Stopping short is always the cause. But to say a country is “stopping short” implies there is some place to get to, some place to arrive at, some eventual goal that is being stopped short of. There isn’t. Unless the goal is to conquer and subjugate the whole world, there is no end. Military expansionism is a doomed policy that must eventually end in grief for the expansionist power. Rome learned that the hard way. 

Yet even now some countries persist in pursuing a policy of military expansionism. Conquering weaker peoples is thrilling and exhilarating, but it’s also a curse. Over the long run it rebounds on the aggressors, and when it does the threat to the aggressor nation is existential.