My thoughts have turned to the many, varied and often tiny Roman border outposts.
Think of the many American Westerns with small and always undermanned frontier forts. The local garrisons were on alert 24-7 against Indian raids targeting local farmers and commercial traffic.
The borders of the Roman Empire were enormous. Protecting Roman citizens from barbarian raids was as close to impossible as you can get.
Doubtless there were thousands of stories to be told of heroism, slaughter and sacrifice, but those stories are all lost to the mists of time.
The grand strategy of the empire was, on the whole, defensive.
The Sahara, Euphrates, Danube, and Rhine were natural frontiers, and it was exceptional when the Romans launched new campaigns of conquest. If territory was added, it was to shorten the frontier, or to improve a vulnerable part of the frontier.
The basic principle of defense was deterrence: wherever the enemy attacked, he would always find a professional, heavily armed Roman force that often outnumbered him. Except for the desert frontier, the limes usually consisted of a clear line where the enemy had to stay away from (e.g., Hadrian's Wall or the river Danube).
However, sometimes the line was attacked. The soldiers in the watchtowers signaled the invasion to the nearby forts. The watchtowers themselves were lost, but the invaders would immediately have to face with Roman forces from nearby forts.
Almost always, this was sufficient to deal with the situation. If the attackers were able to reach and loot a city, they would be massacred on their way home. The final act of every attempt to attack the empire was Roman retaliation against the native population.
The Roman Frontier in Jordan
Built at the beginning of the fourth Century AD and known as Mobene, the walls of Qasr Bashir still stand intact, at a height of up to 20 feet in places, while the main entrance remains to this day. The huge corner towers still rise up two stories from the ground.
It is likely that Qasr Bashir was originally home to an auxiliary cavalry unit, charged with defending the Roman frontier and keeping the peace in the surrounding area.
The Roman Frontier in the East -- Qasr Bashir Fort Reconstructed
The military post of Boreum was about as far from anything that resembled civilization as you could find under either Rome or Byzantium.
I suspect any commander assigned to this remote post was on the shit list in Constantinople. "Here is your new posting. We will relieve you in about 20 years."
The area was so remote that the historian Procopius reports in the 500s that civil servants from Libya who were promoted to posts in Constantinople had problems communicating with government staff. They spoke only Latin and did not speak Greek.
As a frontier town, Boreum was mentioned by Ptolemy of Alexandria about 130 A.D.
The main job of the garrison was to keep inland tribes from causing trouble with the coastal farming communities.
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Around 710, as Muslim armies approached the city, its Byzantine Governor, Julian changed his allegiance, and exhorted the Muslims to invade the Iberian Peninsula.