'I damn well hope he tries!' the governor said, a fierce look crossing his face. 'If he does, we'll deal with him, Primarch Jonson. You mark my words.' With that, he turned on his heel and began snapping orders to his men, and the Dragoons went to work with surprising speed.

The reserve force returned to their start position and the wait began once more. Nemiel stepped outside the Rhino and sat down against its armoured flank, trying to balance his humours and rest his body with meditation. Ten minutes later, the observers called across the command net and said that a large force of armoured vehicles was approaching from the south. Orders were passed along the company command nets, and the Dark Angels readied their weapons.

Twenty minutes later they felt the rumble of the armoured columns reverberating through the earth, drawing closer with every passing moment. Plumes of black petrochem exhaust rose from the midst of the warehouses to the south. Then, the gunners atop the buildings facing the enemy advance began to call out sightings: three columns of heavy tanks and APCs, approaching fast. To Nemiel it sounded like an entire mechanised battalion, heading straight down their throats.

Jonson received the news calmly. 'Lascannon emplacements, target the main battle tanks and open fire at four hundred and fifty metres,' he said.

The range was already so close that the anti-tank lasers opened fire almost at once. Bright red beams shot down the narrow roadways and struck the lead tanks head-on. One of the vehicles exploded with the first hit; another lost one of its treads and ground to a halt. The third tank pressed forward with a gouge scored along the side of its turret. Its battle cannon elevated and fired a high-explosive shell with a hollow boom. The round overshot, flying past the weapons emplacement and crashing into a manufac-torum on the north side of the sector. The Astartes kept firing, sending beam after beam at the tanks, until finally all three were knocked out. Behind the wrecks, the remaining tanks and APCs were forced to retreat and spread out further along the side-lanes before resuming their advance.

The rebel forces came on in a much broader formation this time, their vehicles arrayed in a wide crescent that nearly encompassed the entire southern perimeter. This time the heavy stubbers joined in the battle, raking the enemy APCs with bursts of armour-piercing shells. The enemy responded with battle cannon shells and autocannon bursts, and the air was filled with explosions and blossoms of fire. The Astartes placed their shots with brutal efficiency, aiming for the known vulnerabilities in the armour plating of the battle tanks and destroying half a dozen in the space of just a few minutes. The APCs fared no better under the hail of shells from the heavy stubbers as the armour-piercing rounds found weak spots in their hulls and punched their way inside, wreaking bloody havoc on the troops embarked within. Several shuddered to a halt and exploded as a tracer rounds touched off their fuel cells, until finally the battalion commander ordered the rest of the infantry to dismount and continue the attack on foot. The infantry squads exited their transports and charged across the fifteen-metre open space, only to be cut down by heavy stubbers and disciplined bursts of boltgun fire from concealed Astartes squads.

Twenty minutes after the attack began, the rebel advance faltered and began to withdraw. They left behind twenty knocked-out vehicles and more than two hundred dead soldiers. Three of the Dark Angels' weapons emplacements had been destroyed by battle cannon fire, and three Astartes had been slain. The First Legion could claim victory in the opening engagement, but the battle was only beginning. The Sons of Horus had yet to make an appearance.

Over the course of the next three hours the Dark Angels repulsed five more attacks. Each time the rebels refined their tactics and probed more aggressively around the Astartes' flanks. Each time they drove back the rebels with significant losses, but casualties among the defenders mounted, and with each attack they lost one or more of their few remaining lascannons or heavy stubbers. To Nemiel it felt as though a noose was slowly being tightened around them.

The rebels dropped mortar rounds onto the outskirts of the sector during the third attack, targeting buildings where they knew a heavy weapons emplacement was located. By the sixth attack the enemy APCs were growing bolder, advancing within ten metres of the sector perimeter before being turned back.

An hour passed before the commencement of the seventh attack, allowing the Astartes time to redistribute ammunition and tend their wounded. The Dark Angels' spirits had been restored by the time the first mortar rounds began to fall, and when the rebel tanks and APCs began their advance they opened fire with their few remaining heavy weapons and prepared for close-quarters combat.

This time the rebel tanks and APCs closed in on the perimeter from three sides, and the weight of fire from the defenders wasn't strong enough to stem the tide. The enemy vehicles hit the first defensive line in a score of places; they poured cannon and heavy stubber fire into the manufactories as they pressed deeper, forcing the Astartes to break cover and assault the lumbering vehicles. Within minutes both companies were involved in dozens of squad-level melees, as the Dark Angels came to grips with platoons of heavily-armed infantry.

And then, judging that the decisive moment had come, the Sons of Horus launched their attack.

'Rhinos approaching from the north!'

Nemiel heard the call over the vox and saw the enemy strategy at once. While the rebel infantry had been probing the extent of the Imperial defences, the Sons of Horus had been moving under cover of the attacks in a sweeping movement to the north that would bring them around behind the Dark Angels' positions. It was the kind of swift, decisive strategy that made the Sons of Horus such deadly opponents on the field of battle, and reflected the tactical prowess of their illustrious primarch. Now, Nemiel and the mobile reserve was all that stood in their way.

'Move out!' he ordered as he leapt inside the lead Rhino and slammed the troop door shut. The three transports roared into motion, circling around the assembly building and racing down the accessways to the northern perimeter. He switched to the command net and called the rooftop lookouts. 'How many Rhinos are we facing?' he asked.

'I count four,' one of the lookouts replied. 'The Dragoons are engaging them now.'

The Tanagran troops stood their ground in the face of the enemy charge, and the autocannons of their four Testudos began to spit bursts of armour-piercing rounds at the oncoming transports. Two of the lightly-armoured APCs were hit and ground to a halt, smoke pouring from their wrecked power plants. A third caught fire and exploded, scattering burning debris in a wide arc.

Had the vehicles been crewed by human troops, the attack would have been stopped cold, but the hatches on all three of the destroyed vehicles slammed open and squads of pale-armoured warriors fought their way free of the wreckage and resumed their attack. They were fearsome apparitions of war, their battle-scarred armour clad with two centuries' worth of campaign honours and prized trophies looted from worlds stretching the length and breadth of the Imperium. Once they had been called the Luna Wolves, and had been the first of the Astartes Legions to be reunited with their primarch. Their name had been synonymous with the Emperor's Great Crusade for nearly two hundred years. Now they were called the Sons of Horus, and they had drowned Isstvan III in the blood of twelve billion innocent souls.

Boltguns blazed, wreaking carnage among the Dragoons; plasma guns spat bolts of charged particles that bored into the front armour of the Testudos and blew two of them apart. The lone surviving Rhino continued forwards, firing bursts from its remote-controlled twin bolter until it crashed into the enemy positions and dropped its rear assault ramp. Another squad of rebel Astartes charged out of the vehicle and attacked the surviving Dragoons in close combat, carving through the exhausted soldiers with snarling chainswords and glowing power weapons.