The unmistakable sound of a drum carried across the waves. Its rhythm was rapid, triggering memories of the voyage to Asia Minor. They had been seen.

The rowers at the oars responded to the booming command, and the trireme’s speed began to pick up. It surged forward, creating a large bow wave. The top of the bronze ram at its prow became visible, and even those who had never seen one could guess what the huge mass of metal would do to another vessel.

‘Come about,’ yelled Ahmed. ‘Quickly!’

The two steersmen needed little encouragement. Frantically they leaned on the heavy steering oars, slowing the dhow in the water and beginning a wide turning circle.

Romulus clenched his jaw. It was slow, far too slow. He stared at the trireme’s low-slung shape with morbid fascination. Even faster drumbeats filled the air. The Roman vessel was now in red-hot pursuit. By trying to flee, Ahmed had probably sealed their fate. There was little chance of escape.

From the look on the Nubian’s face, he was thinking the same thing.

‘Time to leave,’ Romulus whispered to Tarquinius, who was muttering a prayer. ‘Ready?’

‘Of course.’

Hastily the two friends donned their armour and tightened their belts. Although Romulus’ mail shirt and Tarquinius’ hide breastplate were heavy, the protection they granted would be needed in the days to come. And it was only a few hundred paces to shore. That distance was nothing to worry about. After four years at sea, Romulus had learned to swim well and Tarquinius was a natural.

The haruspex shoved a water bottle into his hands and together they moved to the side of the ship. They had to act fast. The trireme was already moving significantly faster than their dhow, and over such a short distance, it posed a lethal danger. A hundred and twenty disciplined oarsmen rowing in unison could rapidly bring it to the speed of a running man. If the pirate ship did not complete its turn soon, it would be run down and sunk.

‘You miserable bastard, Tarquinius! Look what you have guided us to!’ shouted Ahmed. He spun round to deliver more abuse. ‘Trying to escape now?’ he screeched, drawing his sword. ‘Kill them both!’

Men’s heads turned, and their faces twisted with fury as they saw two of their erstwhile comrades about to jump ship.

‘Come on,’ urged Romulus, swinging himself up on to the wooden side rail.

The Nubian sprinted across the deck, waving his cutlass and screaming with rage. He was aiming straight for the haruspex – who tripped and fell awkwardly to one knee.

‘Jump!’ shouted Tarquinius.

As Romulus turned back to help his friend, he lost his balance and tumbled backwards – into the sea.

Chapter XXV: Pharsalus

Eastern Greece, summer 48 BC

Brutus reined in his bay horse, which was growing tetchy in the heat. The flies buzzing around its head were no help. ‘Steady,’ he whispered, patting its neck. ‘It will soon begin.’

Around him were six cohorts of legionaries. Like all Caesar’s units, they were understrength, but these were supremely fit, crack troops. Their obliquely angled position to the rear of Caesar’s triplex acies formation belied the importance of their task, Brutus thought proudly. Hidden away, he and his men were Caesar’s secret weapon.

After nearly a week of standoff on the plain of Thessaly, Pompey had finally decided to give battle. Moving away from the foothills to the north that morning, his eleven legions had formed up in three lines, the classic configuration; this was copied at once by Caesar’s nine. Although Caesar’s army matched the width of his enemy’s, the difference in their sizes was already obvious. Weakened by their heavy losses in Gaul, his veteran cohorts were stretched painfully thin. In contrast, Pompey’s were at full complement, meaning he had about forty-five thousand infantry to his opponent’s twenty-two. His cavalry, swelled by volunteers from all over the east, outnumbered Caesar’s by nearly seven to one. The figures were daunting, but Brutus’ general was not about to avoid confrontation. While his army was much smaller than Pompey’s, all Caesar’s legionaries were seasoned fighters; in contrast, many of their opponents were raw recruits.

It was an interesting yet potentially disastrous situation, thought Brutus nervously. Would Caesar’s gamble pay off? Only the gods know, he reflected, asking Mithras for his aid while there was still time. For battle would shortly commence. Both sides were ready now. Pompey’s right flank was protected by the River Enipeus, which ran roughly west-east, while nearly all his superior horse was massed on the left. Today there was to be no classical pincer movement, using cavalry to encircle the enemy on both flanks.

Like any military officer with wits, Brutus knew what was about to unfold instead.

As the opposing legionaries went head to head, the Republican horsemen would drive through Caesar’s small numbers of cavalry, opening up his rear. There they would wreak havoc, cause widespread panic and potentially win the battle. Unless Caesar’s risky venture paid off.

Still nothing happened. The summer sun was climbing in the sky, and although the air was warm, it was nowhere near what it would be by midday. Almost unwilling to fight, the two armies watched each other in silence. When they finally met, Roman would face Roman in unprecedented numbers. Armed and dressed similarly, attacking in the same formations, brothers would fall upon each other while neighbours fought to the death. The momentousness of this confrontation was obvious to even the lowliest foot soldier.

Yet it was time that things were resolved, thought Brutus impatiently. More than eighteen months after Caesar’s crossing of the Rubicon, the two generals had still not fought a decisive battle. Italy was not to be the battlefield, either. Shocked, unprepared for Caesar’s daring, Pompey and most of the Senate had fled from Rome, foolishly leaving the treasury contents in the temple of Saturn. They convened at Brundisium, the main jumping point to Greece, where, furiously pursued by the newly enriched Caesar, they were nearly caught in March. But after an attempt to blockade the port failed, Pompey, his entourage and entire army had made the short crossing without harm.

Brutus smiled. As ever, his leader had not sat around for long.

Keen to secure his rear from the seven Pompeian legions in Hispania, Caesar marched north and west, besieging Massilia and its Republican garrison on the way. The city did not fall quickly so, leaving Brutus and Caius Trebonius to finish the job, he had continued to Hispania. After a frustrating campaign of four months, Pompey’s forces there were finally defeated and assimilated into Caesar’s own. Marcus Petreius and Lucius Afrianus, their leaders, had been pardoned on the condition that they did not take up arms against him again.

Brutus scowled. He would not have been so merciful. ‘Great Mithras, let me meet those treacherous dogs today,’ he muttered. It was unlikely on a battlefield this large, Brutus thought, but he could hope. Petreius and Afrianus were here. The instant they had been released, the pair had gathered what troops they could and sailed to join their master. Two other men whom Brutus badly wanted to meet were Cassius Longinus, the tribune and ex-army officer, and Titus Labienus, Caesar’s former trusted cavalry commander. In a surprise move, they had both switched sides to join the Republicans and were present on the field too. Traitors all, he thought.

Pompey in turn had not been idle while the conflict in Hispania went on, assembling nine legions of Roman citizens in Greece. Added to these were the two veteran legions from Syria, and allied troops numbering three thousand archers from Crete and Sparta, twelve hundred slingers and a polyglot force of seven thousand cavalry. Every city-state ruler and minor prince within five hundred miles had sent a contingent to join the Republican forces.