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H - 176 : ... til there is nothing left to plunder

Trajan's Column in Rome is now topped with a Statue of Saint Peter


A day before reaching Alanya, the ancient pirate nest, we will stop at Selinus (Gazipasa). There, lost in the fields, stands a monument to Roman Emperor Trajan. On his way home from campaigning in Mesopotamia, he died here in 117 AD. Just a year earlier, when standing on the shores of the Persian Gulf, he regretted not being younger. Clearly, he dreamt about conquering India, as Alexander the Great did 400 years earlier. Today, most people remember Trajan from his 38-meter-tall victory column. Erected over the Forum of Traja, it celebrates the victory in Dacia, modern Romania. Trajan’s remains were transported from Selinus to Rome and buried in the basement of his column.

Remains of Trajan's Monument in Selinus (Gazipasa) which was renamed Trajanopolis


Always wondered why Trajan started the war with Persian Parthia (116 – 117 AAD). Why did he want to conquer Mesopotamia? He knew that the Parthians were a formidable foe. Also, why did his successor Hadrian withdrew Roman troops so quickly from Mesopotamia, only one year after Trajan’s death? And why did Trajan commit only 6 of his 30 legions to the war. If the general interpretation of events is correct that Trajan wanted to resolve the Persian question once and for all, would he not commit more than just 20% of his army? His siege of Hatra, one of Parthia’s last strongholds, failed in 117 AD due to fodder for his cavalry and lack of timber to build siege engines. It does not really look like an ”all in” by Trajan.

Map of ancient, double-walled Hatra west of the Tigris

There is a famous saying that the Roman Empire expanded until there was nothing left to plunder. Maybe this applies to Trajan’s conquest of Mesopotamia too? Was there not enough loot to bring home? One of Rome’s biggest heists was the conquest of Egypt by Augustus in 30 BC. With one stroke of luck, he tripled Rome’s annual tax income from 340 million to 1 bn sesterces. The cost for the Roman Empire was minimal. It kept just 2 Legions in Egypt. Under Augustus, 80% of Rome’s budget was consumed by the Army which had 22 Legions plus an equivalent number of auxiliary soldiers. The cost per Legion thus was 18 Million sesterces. Raising 700 million in tax income in Egypt for the cost of 36 million sesterces was a good deal indeed.

Location of Rome's 30 Legions in 100 AD indicated by small, yellow Rhombus


In comparison, Gaul, where 4 Legions were stationed, produced only 40 millions of annual tax revenue. It was a financial loss. Britain was even worse.  With 6 times fewer people, full three Legions were needed to keep the unruly Brits under control. No wonder that Hadrian built the famous wall separating Scotland from the Roman Empire. Controlling the Scots would have required additional 2 Legions. Augustus made a similar decision with respect to Germany. Having lost three Legions in the Teutoburger Forest in 9 AD, he decided that the conquest of Germany was not worth the cost. Occasional raids combined with the Limes would keep the German tribes off balance.  

Failed Roman Invasion of Arabia Felix in 26/25 BC


Roman Emperors were well known for this type of “Return on Investment” thinking. It is best illustrated by Augustus himself. Four years after the conquest of Egypt he ordered the conquest of Arabia Felix, today's Yemen. Lured by rumors of immense wealth, the target was tempting. It was the land were myrrh and frankincense came from. An army of 10’000 soldiers (equivalent to a Legion) set out with 200 ships but eventually achieved nothing and had to withdraw. The logistics were too demanding. The Romans did not lose a single battle but they lost the war. Lacking water, food and timber for siege engines made them fail. For the same reasons Rome did not ventured into the Sahara even though they had heard of the“golden kingdoms” along the Niger river.

The Roman Empire under Trajan when it reached its maximum Extension in 117 AD

Trajan may well have the had Augustus in mind. He wanted to be an emperor as respected as his famous predecessor and go down in history with a similarly big legacy. Still today people talk of the 200 years of Pax Augusta which allowed Rome and its citizens to prosper.


Trajan fought 2 successful military campaigns against the people living in Dacia, today’s Romania. From 101 – 105 AD he defeated the Dacian King Decebalus and conquered his capital Sarmizegetusa.  It was a terrible war. The Romans torched all villages and towns in their way. It would not be farfetched to say that this was a war of extermination. The reason why Romanian is a Latin language today are that thousands of Romans had to be settled in the deserted landscape. Trajan real price was Kine Decebalus’ treasure: 165.5 tons of gold and 330 tons of silver. The silver was equivalent to 110 million, the gold to 660 millions of sesterces. In addition, Rome now controlled the Dacian gold mines which contributed annually 700 million sesterces to the Empire’s tax base. The three Legions required to garrison Dacia cost 54 million sesterces. A good trade for an Emperor’s mind.


Roman Soldiers present Emperor Trajan (left) with the Heads of killed Dacian Leaders

Whether Trajan invaded Parthia in 116 AD for similar reasons is not known. Most historians believe Trajan wanted to destroy the Parthians Empire taking advantage of its civil war. There are good reason for him to attack with only 20% of his forces. The first year confirmed his intuition. He routed the few Parthians who opposed his advance, took their capital Ctesiphon and reached Charax on the Persian Gulf, the capital of the Parthian vassal

Kingdom of Characene.

Charax, founded by Alexander the Great as harbor for Babylon, was an alternative to the Red Sea route from India to the West. Trade goods would ship via the Persian Gulf up the Euphrates and then on camels’ back to Palmyra, the Roman town in Syria. From there it was ten days of caravanning to the Levant. This route was more cumbersome and under the control of the Parthians who - of course - taxed the passing goods. But it was viable and remained so until Ottoman time. It would not surprise me if Trajan thought that controlling this route would provide him and the Roman Empire with another lucrative revenue stream. Egypt was worth 700 million sesterces, Dacia another 700 million. Taxes from Characene must be in the same magnitude.


The Kingdom of Characene was a Parthian Vassal. Charax its harbor on the Persian Gulf

All turned out to be different. Mesopotamia’s wealth was in agricultural products which could not easily be transported to Rome. There was no waterway to the Mediterranean like the Nile. Only desert. Also, Mesopotamia did not have any precious metals like Dacia. Only trade. And last but not least. The volume of trade was significantly lower than what passed through the Red Sea. The Parthian Empire did not have the purchasing power of Rome. Add to this that Rome’s invasion united the Parthians which had withdrawn into the Zagros Mountains from where they attacked and interrupt Roman logistics and communication.


The Parthian Cataphracts, Predecessors to the Medieval Knights, were a big Challenge for the Roman Infantry. The Legionnaires had no effective weapons to defeat them.

Trajan’s successor Hadrian thus had to decide whether to commit more troops and carry the war into the Persian heartland or to withdrew. Mesopotamia would not be a second Egypt tax revenue wise. The cost of its permanent occupation with maybe 12 Legions at annual 216 million sesterces  was undeniable though. And thus too expensive.

Roman Emperor Trajan - 53 - 117 AD


Maybe the saying that “the Roman Empire will stop expanding when there is nothing left to plunder” needs to have the word “easily” inserted. Cost-benefit analysis applied to Roman Emperors as to anybody else.













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