The ambassadors of Julian had been instructed to execute with the utmost diligence, their important commission. But in their passage through Italy and Illyricum, they were detained by the tedious and affected delays of the provincial governors; they were conducted by slow journeys from Constantinople to Cæsarea in Cappadocia; and when at length they were admitted to the presence of Constantius, they found that he had already conceived from the despatches of his own officers, the most unfavourable opinion of the conduct of Julian, and of the Gallic army. The letters were heard with impatience; the trembling messengers were dismissed with indignation and contempt; and the looks, the gestures, the furious language of the monarch, expressed the disorder of his soul. The domestic connection which might have reconciled the brother and the husband of Helena, was recently dissolved by the death of that princess, whose pregnancy had been several times fruitless, and was at last fatal to herself. The empress Eusebia had preserved to the last moment of her life, the warm and even jealous affection which she had conceived for Julian; and her mild influence might have moderated the resentment of a prince, who, since her death, was abandoned to his own passions, and to the arts of his eunuchs.
But the terror of a foreign invasion obliged him to suspend the punishment of a private enemy; he continued his march towards Persia, and thought it sufficient to signify the conditions which might entitle Julian and his guilty followers to the clemency of their offended sovereign. He required that the presumptuous cæsar should expressly renounce the appellation and rank of augustus, which he had accepted from the rebels; that he should descend to his former station of a limited and dependent minister; that he should vest the powers of the state and army in the hands of those officers who were appointed by the imperial court; and that he should trust his safety to the assurances of pardon which were announced by Epictetus, a Gallic bishop, and one of the Arian favourites of Constantius. Several months were ineffectually consumed in a treaty which was negotiated at the distance of three thousand miles between Paris and Antioch; and as soon as Julian perceived that his moderate and respectful behaviour served only to irritate the pride of an implacable adversary, he boldly resolved to commit his life and fortune to the chance of a civil war. He gave a public and military audience to the quæstor Leonas; the haughty epistle of Constantius was read to the attentive multitude; and Julian protested with the most flattering deference, that he was ready to resign the title of Augustus, if he could obtain the consent of those whom he acknowledged as the authors of his elevation. The faint proposal was impetuously silenced; and the acclamations of “Julian Augustus, continue to reign, by the authority of the army, of the people, of the republic, which you have saved,” thundered at once from every part of the field, and terrified the pale ambassador of Constantius.
The situation of Julian required a vigorous and immediate resolution. He had discovered, from intercepted letters, that his adversary, sacrificing the interest of the state to that of the monarch, had again excited the barbarians to invade the provinces of the West.
The hopes of Julian depended much less on the number of his troops, than on the celerity of his motions. In the execution of a daring enterprise, he availed himself of every precaution, as far as prudence could suggest; and where prudence could no longer accompany his steps, he trusted the event to valour and to fortune. In the neighbourhood of Bâle he assembled and divided his army. One body, which consisted of ten thousand men, was directed under the command of Nevitta, general of the cavalry, to advance through the midland parts of Rætia and Noricum. A similar division of troops, under the orders of Jovius and Jovinus, prepared to follow the oblique course of the highways, through the Alps, and the northern confines of Italy. The instructions to the generals were conceived with energy and precision; to hasten their march in close and compact columns, which, according to the disposition of the ground, might readily be changed into any order of battle; to secure themselves against the surprises of the night by strong posts and vigilant guards; to prevent resistance by their unexpected arrival; to elude examination by their sudden departure; to spread the opinion of their strength, and the terror of his name; and to join their sovereign under the walls of Sirmium.