"For what?"
"I'm not sure, but the men posted on the other side of the hill are whooping and cheering. Something's happening down in the harbor."
"Show us the way!" barked Antony. I hesitated to follow, uncertain of my place now that we had reached the theater of battle. Antony peered back at me. "Aren't you coming, Gordianus?"
We rode to the top of the low hill, where several tents had been pitched and a sizable contingent of soldiers had been posted as lookouts. Toward the north, in the direction we had come, the site commanded a sweeping view of the beach and the coastal road for miles. The centurion had seen us approaching for hours.
Toward the south, the site overlooked the city, the harbor, and the sea. The centurion led us to a vantage point with an unobstructed view. "They say this was the very spot where Caesar stood, when he planned the siege," he said proudly.
The walled city of Brundisium is situated on a peninsula surrounded by a semicircular harbor. A narrow strait links this protected harbor to the Adriatic Sea. The easiest way to visualize the city, as it might appear on a map, is to hold up your right hand and form a reverse letter C. The space enclosed by your forefinger and thumb represents the peninsula upon which the city is built. Your forefinger and thumb represent the northern and southern channels of the harbor. Your wrist represents the strait through which ships must sail to reach the sea.
From our vantage point, the city on the peninsula appeared as a cluster of tenements, warehouses, and temples crowded within high walls. Pompey's soldiers were clearly visible on the towers and parapets, their helmets and spears glinting in the westering sun. Along the landward western wall, which ran between the north and south channels of the inner harbor, the besieging army of Caesar was encamped. The force appeared to my eye enormous. Row upon row of catapults and ballistic machines had been assembled, along with several siege towers on wheels, which rose even higher than the city walls.
But I saw nothing to cause a commotion among the watchers on the hillside. The siege towers and war machines were unengaged. No smoke rose from the city, and I saw no sign of fighting along the wall.
"There!" Antony pointed away from the city, toward the entrance to the harbor and beyond. A fleet of large ships was approaching from the open sea. Several had already reached the harbor entrance and appeared to be maneuvering to sail through in single file. I found this curious, as I had sailed in and out of Brundisium myself in the past, and knew that the harbor entrance was deep and wide enough for several ships to sail abreast, yet these were apparently endeavoring to enter one at a time, keeping as close to the center as possible.
As the first ship entered the straits, I saw the reason for such a course. The sight was so strange, I had trouble believing my eyes. At the narrowest part of the entrance to the harbor, great piers of some sort had been built out from both promontories, extending far into the water. This breakwater very nearly met in the middle, or so it appeared at a distance, almost closing off the entrance to the harbor. Short towers had been built at intervals along both arms of the structure, and these were equipped with catapults and ballistic machines.
"By my ancestor Hercules, what are we seeing?" muttered Antony, as puzzled by the sight as I was. He turned his head and scanned the other soldiers watching along the hillside. A bearded little fellow was standing atop a boulder nearby, viewing the scene intently with his arms crossed, mumbling to himself. Antony called out to him. "Engineer Vitruvius!"
The man blinked and looked in our direction.
"Engineer Vitruvius! Report!"
The man scrambled down from the rock and came running. He saluted Antony. "Tribune, you've rejoined us!"
"You state the obvious, Marcus Vitruvius. What's not so obvious is what we're witnessing down there. What in Hades is going on?"
"Ah!" Vitruvius looked toward the harbor, but was so short that the tops of some trees down the hillside blocked his view. "If we may retire to higher ground, Tribune…"
We followed him back to the boulder. He scrambled atop it, crossed his arms, and gazed down at the harbor. "Now, Tribune, if I may explain the situation…" His tone was typical of the condescending manner of builders and engineers even when dealing with superiors, if those superiors know less than they do of construction and mathematics.
Vitruvius cleared his throat. "Seven days ago we arrived outside Brundisium. Caesar moved at once to encircle the city and the harbor, placing the greatest part of his six legions before the city wall but also securing the promontories north and south of the harbor entrance. Our commander hoped to trap not only Pompey but also the two consuls and the many senators with him, so as to force immediate negotiations and a settlement of the crisis."
"But…" prompted Antony.
"A bad sign: our advance intelligence indicated that Pompey had assembled a considerable fleet, yet there were only a few ships in the harbor. Where had the fleet gone? Alas, before we arrived, Pompey had already sent the consuls, senators, and a substantial part of his army across the Adriatic to Dyrrachium, out of harm's way. Always seeking peace, our commander endeavored to negotiate directly with Pompey. The Great One sent back word that no lawful settlement could possibly be concluded in the absence of the consuls. Hence, no negotiations."
"Our intelligence from within Brundisium- Pompey has treated the locals with contempt and they're eager to help Caesar- informed us that Pompey kept twenty cohorts with him. Not to hold the city indefinitely- how could he, with only twelve thousand men against three times that number?- but long enough for his fleet to reach Dyrrachium, unload the first round of passengers, then return to Brundisium to pick up Pompey and his men."
"Our commander, having pursued Pompey this far, had no intention of allowing him to slip away. He came to me. 'They must be stopped, Engineer Vitruvius! We must prevent Pompey's ships from reentering the harbor when they return, or if they manage to do so, we must prevent them from leaving. But I have no ships of my own, and my men cannot march on water. This strikes me as an engineering problem, Marcus Vitruvius. Can you blockade the harbor?' I said I could. 'Then make it thus, Engineer Vitruvius!' "
The little man waved his arm in the direction of the harbor. "You can see the result from here. We began by building great breakwaters of earth and stone on either side of the harbor entrance, where the water is shallow. Unfortunately, as the work progressed and we reached deeper water, it became impossible to keep the earthworks together. At that point we built a raft, thirty feet square, at the end of each breakwater and moored each raft with anchors at all four corners to keep them still in the waves. Once these platforms were in position, we added more rafts, joined them firmly together and covered them with a causeway of earth, so that they were as steady as an actual breakwater, even though they float atop the waves. If you squint, you can see that screens and mantlets have been put up all along both sides of the causeways to protect the soldiers coming and going. On every fourth raft we constructed a tower two stories high, to defend against attacks by sea. The goal, of course, was close off the harbor completely."
Antony grunted. "All this was your idea?"
Vitruvius beamed. "Actually, if you believe the Greek historians, Xerxes the king of Persia did something like this when he bridged the Hellespont and led his army from Asia into Europe. I've always wondered how such a feat was accomplished. I suspect he must have used a similar technique, anchoring rafts and linking them together."
Meto had often told me of great feats of engineering conjured by Caesar in his battles against the Gauls. Under Caesar's command, men bridged rivers and chasms, dug vast trenches and canals and tunnels, and constructed great towers and siege engines. But an attempt to close off a harbor was something new.