As the United States is finding out with some regularity, it is not easy to defeat an enemy that avoids battles. Targeting such an enemy is difficult not because it is technically complicated but because it is strategically of limited use: we can chase and sometimes hit a few targets, but these actions often have little impact on the wider problem, which allows the enemy simply to reappear elsewhere. War turns into a frustrating whac-a-mole game from the tactical to the strategic level, as the enemy vanishes on one street and reappears on another in a slightly different form and with a different set of tools. As the enemy spreads violence, or even just the possibility of violence, across a large geographic area, it sows instability undermining the authority of the ruling power.

The problem is not new.

 

Consider, for example, the war of Tacfarinas, a relatively forgotten and minor conflict described with keen insight by one of the world’s greatest historians, Tacitus, in his Annales. This war occurred in the first decades of the 1st century AD in North Africa (15-24 AD), where Roman influence was spreading rapidly and rubbing against local tribes, who were naturally uneasy about a distant power extending its dominion over their territory. Rome was limiting the movement of local tribes, imposing taxes, and establishing boundaries and property rights on land, in the process forcing many of the locals to alter their semi-nomadic lifestyle. But regardless of the motivations for the rebellion, the way it took shape is instructive.

 

There were three distinct moments, characterized by a learning contest between the rebels and the Romans, in this conflict.

 

First, Tacfarinas, a member of a Numidian tribe, “deserted from service as a Roman auxiliary” (Annales, II:52) and began to gather around him marauders who were interested in looting. Like many other of the most lethal enemies of Rome (notably, the Germanic leader Arminius, a Roman citizen and soldier, who tricked a Roman commander, Varus, and three of his legions into marching into an disastrous ambush in the Teutoburg forest in 9 AD), Tacfarinas had learned martial skills in one of the many indigenous or auxiliary units that fought alongside Roman legions. Intimately familiar with Roman tactics and operations, he turned his expertise against his former ally. He quickly organized his own forces into formations and units, probably mimicking Roman legions, and became the leader not of a disorganized mob (inconditae turbae) but of the Musulamian people. More tribes joined Tacfarinas, who kept an elite part of his new army in encampments where he trained them in discipline and obedience (and armed them like Romans). Another part of the army, less Roman-like, was left to raid the surrounding territories and instill terror.

 

But this was a big mistake. The Numidians, thinking that Roman arms and organization made them…