This celtic x roman thing reminded me of a quote:
"Yet it was not the “barbarian” advance but the Roman that was truly inhuman and chilling. The legions, as the Christians did at Lepanto and the British at Rorke’s Drift, fought in silence; they walked until the last thirty yards of no-man’s-land. At a predetermined distance the first line threw their seven-foot pila, for the first time yelling in cadence as they unleashed the volley. Immediately and without warning, hundreds of the enemy were impaled, or their shields rendered useless by the rain of projectiles. Now with the lethal short swords unsheathed, the first rank crashed into the stunned enemy mass. The oblong shields had iron bosses in the centers, and the Romans used them as battering rams to shock the enemy, as the well-protected legionaries hacked off arms, legs, and heads during the confusion. Individual soldiers pushed in to exploit gaps where the dead and wounded had fallen. Almost immediately, an entire second army, the succeeding line of principi, surged in to widen the tears in the enemy line, hurling their pila over their friends’ heads in the melee, the entire process of charging, casting, and slicing now beginning anew— with yet a third wave ready at the rear.
The terror of war does not lie in the entirely human reaction of tribal cultures to bloodletting—screaming and madness in giving and receiving death, fury of the hunt in pursuit of the defeated, near hysterical fear in flight—but rather in the studied coolness of the Roman advance, the predictability of the javelin cast, and the learned art of swordsmanship, the synchronization of maniple with maniple in carefully monitored assaults. The real horror is the entire business of unpredictable human passion and terror turned into a predictability of business, a cold science of killing as many humans as possible, given the limitations of muscular power and handheld steel. The Jewish historian Josephus later captured that professionalism in his chilling summation of legionary prowess: “One would not be wrong in saying that their training maneuvers are battles without bloodshed, and their battles maneuvers with bloodshed” (Jewish War 3.102–7).
The utter hatred for this manner of such studied Roman fighting surely explains why, when Roman legions were on occasion caught vastly outnumbered, poorly led, and ill deployed in Parthia, the forests of Germany, or the hills of Gaul, their victors not only killed these professionals but continued their rage against their corpses—beheading, mutilating, and parading the remains of an enemy who so often in the past could kill without dying. The Aztecs also mutilated the Spanish—and often ate the captives and corpses; and while this was purportedly to satisfy the bloodlust of their hungry gods, much of the barbarity derived from their rage at the mailed conquistadors, with their Toledo blades, cannon, crossbows, and disciplined ranks, who had systematically and coolly butchered thousands of the defenders of Tenochtitlán. In the aftermath of the British defeat at Isandhlwana, the Zulus decapitated many of the British and arranged their heads in a semicircle, in part because so many of their own kinsmen had minutes earlier been blown apart by the steady firing of Martini-Henry rifles."