The Persians were advancing sensibly, coming on in good order. The main body was advancing at the speed at which the ballistae could be moved. The mantlets, which could be transported considerably faster, were staying with the artillery to try to shield them. The three great siege towers were lagging quite some distance behind.
Ballista's eyes were concentrated on the two white stones 400 paces away. He held a piece of bread and cheese in one hand and a jug in the other, both completely unconsidered. When the Persians passed the stones, they would have to advance for 200 paces into the teeth of the artillery on the town wall. Hauling their artillery forward, for those 200 paces the Sassanids would be unable to hit back. The northerner had ordered his artillery to concentrate exclusively on the enemy ballistae and the men moving them. Initially, little could be expected – the range was too great for any accuracy – but things should improve as the slow-moving targets came closer. Knock out as many of them as we can before they can get at us. With luck, the stone-throwers would wreck some enemy engines. The bolt-throwers could not damage the ballistae themselves, but they could kill and alarm the men moving them and this would slow down their progress, keep them longer unable to strike back, longer exposed to the stone-throwers on the town wall.
Ballista nodded to Antigonus. The standard-bearer raised the red flag. Twang – slide – thump, twang – slide – thump: up and down the wall the artillery opened up.
The first volley achieved nothing and after a couple of minutes there was no semblance of volley shooting. The crews of the artillery pieces worked at different speeds. Ballista was far from convinced that the quickest were necessarily the best – better to take a little extra time and aim well. It cost him some effort not to take over the laying of the big twenty-pounder next to him. The northerner went to scratch his nose, found a jug in one hand, food in the other. He drank and ate.
Cheers, loud cheers, from the wall off to the right. Ballista looked just in time to see a wheel spinning in the air like a tossed coin. A cloud of dust rose from the plain. Small, brightly clad figures staggered out of it. One of the stone-throwers towards the north of the wall had scored a direct hit. One Sassanid ballista down, nineteen to go.
More cheers, this time off to the left. Ballista could not see the cause. Maximus pointed. 'There! There! Gods below, that's fucked him.' Ballista followed the direction of the Hibernian's outstretched arm. Way, way out from the wall, way out behind the main body of the Persians, was the southernmost of the three siege towers. The great Sassanid City Taker was leaning drunkenly forward, its front wheels deep in the ground.
'Tyche,' said Mamurra. 'I do not think that we dug any pits that far out. Its weight must have made it go through into one of the very furthest out of the old underground tombs. Anyway, they will not get that brute out again today.'
Any battle, like anything in nature, goes in phases. Now for a time the tide was with the defenders, and good news flowed in. As Ballista finished his bread and cheese two messengers treading on each other's heels ran up the steps to the top of the gatehouse.
While the first spoke Ballista passed the jug from his own hand to the other waiting messenger.
The Sassanid attack on the north wall had come to nothing. A great mass of men – it was reckoned there were about 5,000 of them – had been drawing up on the plateau north of the ravine. They were still a very long way off, at the very limits of artillery range, when Centurion Pudens ordered the bolt-thrower on the postern tower to try a shot at them. The ballistarius, more in hope than expectation, had aimed at the leading rider, a richly clad man on a gloriously caparisoned horse. The bolt had taken the Sassanid off the horse easy as could be, left him pinned to the ground. Their leader dead, the reptiles had swarmed away.
Ballista thanked the messenger, and gave him some coins. The other handed the jug over to his colleague and told his news.
The Persians, from somewhere, had got together five boats and crammed about 200 men into them. Stupidly, they had followed the western bank of the river down to Arete. As soon as the boats came into range of the bolt-throwers on the two north-eastern towers, the boatmen, local men who had been pressed into service, dived over the sides, swam to shore and deserted. From then on the boats were in utter confusion. They were little better than drifting while being shot at from the elevation of the walls by bolt-throwers and bowmen. When eventually they tried to land near the fish market, they were easy targets for at least ten artillery pieces and no fewer than 500 archers from the numerus of Anamu. Three of the boats capsized; one foundered just short of the nearest island in the Euphrates; one drifted away downriver. Most of those not killed by missiles were drowned. Only about twenty seemed to have escaped downriver, and another twenty or so were stuck on the island.
As the tale ended, with the Sassanids on the island, Antigonus looked enquiringly at Ballista, who enigmatically said yes, adding, if they were all still around that night. The northerner thanked the messenger and again parted with some coins.
But the tide cannot flow one way for ever. All too soon, and at the cost of only one more ballista, the Sassanid artillery had crossed their zone of impotence. They had reached their intended shooting positions just within effective range. Persians swarmed about, dismounting the artillery from their rollers, setting up protective screens, putting the ammunition to hand, winching back the sliders, placing the missiles, aiming and releasing.
Ballista felt a slight tremor run through the gatehouse as a stone struck. The time of carefree observation was over. Now the air had become a thing of menace; everywhere the tearing, ripping noises of missiles. To the right a man screamed as a bolt shot him from the wall walk. To the left a short section of battlements exploded in stone splinters as a missile struck. A man lay in the middle of the debris moaning. Another lay silent. Passing the word for carpenters to erect a makeshift battlement, Ballista reflected that, other things being equal, the defenders should win this exchange of artillery. They had twenty-five ballistae to eighteen, and the advantages of a higher position, as well as stone, not wooden, walls for protection.
Yet other things were not equal. The two City Takers remaining mobile had crept forward into maximum artillery range. Just when the enemy would be shooting back, the northerner was going to have to order his ballistarii to change targets. As they came in range, the huge siege towers would be the sole targets. Now it would be the turn of the defending artillerymen to endure shot without being able to return it; there can be little worse for any soldier. About to send off the runners to give the order, Ballista added that any ballistarius who aimed at anything other than one of the siege towers once they were within range would be flogged to death. Allfather, the exercise of power has corrupted my soul.
Leaving their ballistae 200 paces from the wall, the main body of Persians huddled as close as possible behind the line of mobile shields. Men fell to traps underfoot and arrows slicing down from above. Yet to the defenders it seemed no time at all before the line of mantlets was established a mere fifty paces from the walls and the Persian bowmen were bending their bows. Ten, twenty, thirty thousand arrows; it was impossible to guess. Like a shadow passing over the face of the sun, they made the day grow darker.
All along the wall, and behind it, the arrows fell as thick as hail in the deep midwinter. On the wall, and in the streets and alleys behind, men fell. The archers on the wall shot back. The defenders had some advantages: they were higher up, well protected by stone crenellations and the stout shields of the legionaries; almost all their arrows found their mark – so vast was the number of Sassanids that they formed a dense target and the mantlets could not shelter them all. But it was an unequal contest: fewer than 650 bowmen against innumerable thousands.