Under the faith of the treaty of Margus, a free market was held on the northern side of the Danube, which was protected by a Roman fortress, surnamed Constantia. A troop of barbarians violated the commercial security; killed or dispersed the unsuspecting traders, and levelled the fortress with the ground. The Huns justified this outrage as an act of reprisal; alleged that the bishop of Margus had entered their territories, to discover and steal a secret treasure of their kings; and sternly demanded the guilty prelate, the sacrilegious spoil, and the fugitive subjects who had escaped from the justice of Attila. The refusal of the Byzantine court was the signal of war; and the Mœsians at first applauded the generous firmness of their sovereign. But they were soon intimidated by the destruction of Viminiacum and the adjacent towns; and the people was persuaded to adopt the convenient maxim that a private citizen, however innocent or respectable, may be justly sacrificed to the safety of his country. The bishop of Margus, who did not possess the spirit of a martyr, resolved to prevent the designs which he suspected. He boldly treated with the princes of the Huns; secured, by solemn oaths, his pardon and reward; posted a numerous detachment of barbarians in silent ambush on the banks of the Danube; and, at the appointed hour, opened with his own hand the gates of his episcopal city. This advantage, which had been obtained by treachery, served as a prelude to more honourable and decisive victories.