Both Roman generals and modern historians have tended to find Julian's moves in the civil war of AD 361 hazardous as well as difficult to understand. This is especially true of his long, ultra-rapid and semi-clandestine journey down the Danube, which was carried out by a dangerously small corps (under the command of the Usurper himself !) and ended with a very brief visit to Sirmium. A competent and, otherwise, cautious general, Julian must have had strong reasons for the risky haste that led him to Sirmium. These reasons were not primarily of a military nature, though enlistment of fresh troops and formation of vexillationes was among the measures he undertook/ initiated in the Pannonian metropolis. A (neglected) passage (13. 287 a) of his Letter to the Athenians (? mainly written during the river journey but sent from Sirmium itself) implies that his visit to Sirmium was chiefly caused by his urgent need to secure the rich mines of precious metals managed by that city (mines situated in the Drinus valley and the Mt. Cer area), as well as silver and gold objects (coins, ingots, plates etc.) stored in Sirmium, which had a mint and the metal officinae of its own. All this would help him i.a. distribute the donativa, already promised to his soldiers and officers. Analogous strategies, inspired by the old experience that the pecunia and/or metalla is/are nervus belli civilis, left traces in the sources describing the wars between Constantine I and Licinius, Vitellius and Vespasian, Otho and Vitellius — to cite the most illustrative examples only.
