Even though the source of the outbreak is still a mystery, its events are meticulously recorded. A plague of zombies swept through the local villages. The local barbarian chieftain and his men, not knowing what they were dealing with, wrongly thought the undead were merely insane, and thus no real threat. Over 3,000 Pictish and Celtic warriors were sent to deal with the "mad uprising". In a series of disorganized fights with the ghouls, about 600 warriors were totally devoured, while the remaining 3,000 wounded warriors were turned into the living dead, including the chieftain. A Roman merchant traveling through the area, Sextus Sempronios Tubero, witnessed one of the battles. While he didn't know the exact nature of the undead, he noticed that decapitation appeared to be the only method that could stop the creatures. Barely escaping with his life, Tubero made it to the nearest Roman installation, and reported his findings to the commander, Marcus Lucius Terentius. It turned out that more than 9,000 ghouls were moving south, following fleeing refugees toward Roman territory, and Terentius had only one cohort, about 480 men, to stop them . The zombies were less than a day away, so Terentius got to work immediately. He drafted a force of civilian laborers who dug relinforced palisades, and two seven-foot-deep, inwardly narrowing ditches that eventually straightened to form a straight, mile-long corridor. The ditches were lined with stakes and filled with bitumen liquidum (crude oil: common for heating lamps in this part of Britannia). The fortifications were finished just as the undead drew near. As the ghouls drew near, Terentius ordered the trench lit. All zombies who fell into the trench were impaled on the stakes or trapped in its confines and incinerated. The rest of the zombies were forced into the narrow choke point of the funnel, where the outnumbered Romans were able to draw swords, raise shields and face their undead enemy. The battle lasted for nine hours, until dawn, when the last zombie heads were rolled into the ditches and cremated. All zombies were destroyed, and only 150 Romans were killed. There were no wounded among the Romans, knowing the nature of the contagion, the legionaires killed any of their number who were bit. The knowledge learned that day were compiled into one comprehensive work known as Army Order 38, or XXXVIII, which Emperor Hadrian ordered to be incorporated into standard Roman military doctrine, and taught to every unit in the Empire. Included within Army Order 38 was not only information about zombie behavioral pattern and how to efficiently dispose of them, it also recommended overwhelming numerical force “to deal with the inevitable panic of the general populace.”It is also said that the outbreak prompted the Emperor to construct the massive "Hadrians Wall" across the northern border of Roman Britain, to guard against an enemy that might well return.