The question regards the highlighted words in this clause from Edward Gibbon.
and Rome was saved, if the wisdom of Belisarius had not been defeated by the misconduct of his officers.
What is it in mood and tense?
I want to say that
- was is subjunctive in mood and present in tense (an equivalent of German wäre except that German itself might have used a form of werden for passivizing) and
- a poetic/rhetorical substitute for had been, which would be subjunctive in mood and past in tense and the thing one should have expected (barring a conditional).
For context, the relevant paragraph.
The foresight of Totila had raised obstacles worthy of such an antagonist. Ninety furlongs below the city, in the narrowest part of the river, he joined the two banks by strong and solid timbers in the form of a bridge, on which he erected two lofty towers, manned by the bravest of his Goths, and profusely stored with missile weapons and engines of offence. The approach of the bridge and towers was covered by a strong and massy chain of iron; and the chain, at either end, on the opposite sides of the Tyber, was defended by a numerous and chosen detachment of archers. But the enterprise of forcing these barriers, and relieving the capital, displays a shining example of the boldness and conduct of Belisarius. His cavalry advanced from the port along the public road, to awe the motions, and distract the attention of the enemy. His infantry and provisions were distributed in two hundred large boats; and each boat was shielded by a high rampart of thick planks, pierced with many small holes for the discharge of missile weapons. In the front, two large vessels were linked together to sustain a floating castle, which commanded the towers of the bridge, and contained a magazine of fire, sulphur, and bitumen. The whole fleet, which the general led in person, was laboriously moved against the current of the river. The chain yielded to their weight, and the enemies who guarded the banks were either slain or scattered. As soon as they touched the principal barrier, the fire- ship was instantly grappled to the bridge; one of the towers, with two hundred Goths, was consumed by the flames; the assailants shouted victory; and Rome was saved, if the wisdom of Belisarius had not been defeated by the misconduct of his officers. He had previously sent orders to Bessas to second his operations by a timely sally from the town; and he had fixed his lieutenant, Isaac, by a peremptory command, to the station of the port. But avarice rendered Bessas immovable; while the youthful ardor of Isaac delivered him into the hands of a superior enemy. The exaggerated rumor of his defeat was hastily carried to the ears of Belisarius: he paused; betrayed in that single moment of his life some emotions of surprise and perplexity; and reluctantly sounded a retreat to save his wife Antonina, his treasures, and the only harbor which he possessed on the Tuscan coast. The vexation of his mind produced an ardent and almost mortal fever; and Rome was left without protection to the mercy or indignation of Totila. The continuance of hostilities had imbittered the national hatred: the Arian clergy was ignominiously driven from Rome; Pelagius, the archdeacon, returned without success from an embassy to the Gothic camp; and a Sicilian bishop, the envoy or nuncio of the pope, was deprived of both his hands, for daring to utter falsehoods in the service of the church and state.