They marched in silence, stopping occasionally to listen out for the Scythians. At last a familiar rectangular shape appeared out of the gloom. It was the fort.

A tiny sigh of relief escaped Romulus’ lips. He was colder than he could ever remember being. But once they were inside and warmed through again, Tarquinius might reveal what he had seen. The desire to know more was the only thing that had kept him going.

Brennus grinned. Even he was looking forward to a break.

On either side of the massive front gates sat a wooden guard tower. They were matched by similar ones on the corners and smaller observation posts in between. The walls had been constructed from closely packed earth, a useful by-product from the construction of the three deep ditches which surrounded the fort. Filled with spiked iron caltrops, the fossae were also within range of missiles thrown or fired from the timber walkway that ran along the inside of the ramparts. The only passage through them was the beaten-down dirt track to the entrance in the middle of each side.

They tramped down it, expecting to be challenged at any moment.

Surprisingly the huge fort was not a fighting structure: legionaries did not hide behind the protection of walls by choice. The impressive defences were to be used only in the case of unexpected attack. If an enemy presented itself, the officers would marshal the men together on the intervallum, the flat area that ran around the inside of the walls, before marching out to do battle. On open ground, the legionary was the master of all other infantry. And with Tarquinius’ tactics and training, thought Romulus proudly, they could withstand the charge of any force, mounted or on foot.

Man for man, the Forgotten Legion could defeat any enemy.

‘Stop.’ Moving to Brennus’ side, Tarquinius checked Pacorus’ pulse.

‘Is he still alive?’ asked the Gaul.

‘Barely,’ answered Tarquinius, frowning. ‘We must hurry.’

Reality struck as Romulus took in Pacorus’ ashen features. Enough time had passed for the scythicon to do its deadly work. The commander would surely die soon and, as the sole survivors, they would be held responsible. No senior Parthian officer worth his salt would fail to punish the men who had allowed this to happen. They had escaped the Scythians to face certain execution.

Yet Tarquinius had wanted to save Pacorus. And Mithras had revealed a road back to Rome.

As a drowning man clings to a log, Romulus held on to those thoughts.

They were now less than thirty paces from the gate and within range of the sentries’ pila. Still no challenge had been issued to check their progress, which was most irregular. No one was allowed to approach the fort without identifying themselves.

‘The lazy dogs will be huddling around the fire,’ Romulus muttered. Sentinels were only supposed to stay in the warm guardroom at the base of each tower for short periods; just enough to thaw out numb fingers and toes. In practice, they did it as long as the junior officer in charge allowed.

‘Time to wake them up then.’ Raising his axe, Tarquinius stepped forward and repeatedly hammered the butt on the gate’s thick timbers. It made a deep thumping noise.

They waited in silence.

The Etruscan had raised his weapon to demand entrance again when suddenly the distinctive sound of hobnailed sandals clattering off wood reached them from above. As expected, the sentry had not been at his post in the tower. A few moments later, a pale face appeared over the ramparts.

‘Who goes there?’ Fear filled the man’s voice as he peered down at the small group. Visitors to the fort were rare, let alone in the middle of the night. ‘Identify yourselves!’

‘Open up, you fool!’ shouted Romulus impatiently. ‘Pacorus has been injured.’

There was a disbelieving pause.

‘You piece of shit!’ cried Tarquinius. ‘Move!’

The sentry’s shock was palpable. ‘Yes, sir! At once!’ He turned and fled down the staircase to the rooms below, roaring at his comrades.

Moments later the heavy locking bar was being lifted. One of the doors creaked open, revealing several legionaries and an anxious optio. The delay in responding would surely result in some kind of punishment.

But Tarquinius pushed past without a word. Romulus and Brennus followed. Confusion filled the sentries’ faces as they took in the prone shape on the Gaul’s shoulder.

‘Shut the gate!’ Tarquinius bellowed.

‘Where are Pacorus’ warriors, sir?’ asked the optio.

‘Dead,’ snapped Tarquinius. ‘We were ambushed by Scythians at the Mithraeum.’

Shocked gasps met this comment.

Tarquinius was in no mood to reveal more. ‘Advise the duty centurion and then get back to your posts. Keep your eyes peeled.’

The optio and his men hastened to obey. Tarquinius was also a centurion and could have punished them as severely as Pacorus. They would have to find out what had happened later.

Tarquinius hurried down the fort’s main street, the Via Praetoria. Romulus and Brennus followed. On both sides lay parallel rows of long, low wooden barracks, each housing a century of eighty soldiers. Their interiors were identical: large rooms for the centurion, smaller ones for the junior officers and more cramped quarters for the men. Ten contubernia, each of eight soldiers, shared just enough space to fit bunk beds, their equipment and food. Like gladiators, legionaries lived, slept, trained and fought with each other.

‘Romulus!’

Hearing the low shout, he half turned. In the shadows between two of the barrack buildings, Romulus picked out the features of Felix, one of his original unit. ‘What are you doing up?’ he demanded.

‘Couldn’t sleep,’ Felix replied with a grin. He was already dressed and armed. ‘I was worried about you. What’s going on?’

‘Nothing. Go back to bed,’ replied Romulus curtly. The less anyone else had to do with this, the better.

Instead, Felix darted to Brennus’ side, gasping when he saw the arrows jutting from Pacorus’ flesh. ‘Gods above,’ he breathed. ‘What happened?’

Romulus filled him in while they marched. Felix nodded, grimacing as he heard the details. Though smaller than Romulus and weaker than Brennus, the little Gaul was a fine soldier. Truly stubborn too. When their mercenary cohort had been cut off during the battle at Carrhae, Felix had stayed by their side. Completely surrounded by Parthian archers, just a score of men chose to remain with the three friends and Bassius, their centurion. Felix was one of them. He’s his own master, thought Romulus, glad to have him along.

No one else halted the small party. It was still dark, and most men were asleep. Besides, only a more senior officer would dare question Tarquinius, and none of those were to be seen. At this time of night, they were also in bed. Soon they reached the principia, the headquarters. This was at the intersection of the Via Praetoria with the Via Principia, the road that ran from the east wall to the west, dividing the camp into four equal parts. Here also were Pacorus’ luxurious house and more modest ones for the senior centurions, the Parthian officers who each commanded a cohort. There was a valetudinarium, a hospital, as well as workshops for carpenters, cobblers, potters and a multitude of other professions.

Tradesmen and engineers as well as soldiers, the Romans were almost self-sufficient. It was one of many things that made them so formidable, thought Romulus. Yet Crassus had managed to expose the Republican army’s sole weakness. It retained almost no cavalry, while Parthia’s forces consisted of little else. Tarquinius had spotted this long before Carrhae, followed soon after by Romulus. But ordinary soldiers had no say in tactics, he reflected angrily. Crassus had marched arrogantly into disaster, unwilling or unable to see what might happen to his men.