u/DauntlessAkagi

During the Tau 3rd Sphere Expansion, the Imperium noticed that the number of planets that were falling to internal pro-Tau rebellions far exceeded the number of worlds directly conquered by the Tau military. In this scene, the Chapter Master of the Raven Guard (Corvin Severax), an Inquisitor and a High Magos assigned to the forces meant to counter the Tau invasion meet to discuss why this is happening.

I think this scene shows how even supposedly intelligent and high ranking members of the Imperium are susceptible to institutional blindness and have a hard time understanding what is obvious to the average person.

‘We (the Raven Guard) will choose our battleground, not they. Already we have lost too many men battling over Agrellan. The tau are closer to home than we. They will likely exhaust their empire to take it. Small as it is, the tau’s domain is vibrant, and confident. Lose here, and we lose the entire subsector. By the time a new crusade is prepared, they will be fortified and ready. We will melt away, and draw them where we will. Elsewhere, we will break their assault, crush their main forces in a battle of our choosing, and then reclaim what is rightfully the Emperor of Mankind’s.’

‘My lord,’ I say. I am astonished that such information is shared with me.

‘I am telling you this, brother-sergeant, because Lord Severax wishes you to go to the surface. Take your squad. You are to seize one of their number and deliver him to Inquisitor Gallius and High Magos Biologian Tulk here.’

‘You wish me to snatch one of their leader caste? I… Consider it done, shadow captain! I will…’

Lord Severax chooses to speak. He leans forward in his throne, armoured hands gripping the carven rests. I see his face fully. His skin is as white as snow, his hair blacker than midnight.

‘You presume too much,’ he admonishes me. His voice is little more than a whisper, but his criticism cuts me. I bow my head, I hang upon his every word.

‘Capturing their ethereals is nigh on impossible. Every attempt that has been tried has failed with great loss,’ said Severax. ‘They will fight to the last to protect them. This task of which you speak we will save for another day. No. Your target is one of their emissaries. You will take one of them, and bring him to us, so that he might reveal the secrets of their persuasiveness.’

He falls silent again.

‘Our forces are sufficient to win this war, but we are losing many more worlds to the efforts of their diplomatic core than we are to military action,’ continues Shrike. ‘We are to be granted no more reinforcement for the foreseeable future. We cannot afford to become committed in one place, while their emissaries talk the worlds of the Emperor out of His light. Capture one of these emissaries while they are distracted. While we are evacuating, you will be on Agrellan. This is a great honour.’

‘We feel that they must have some kind of psychic or chemical hold over those they approach. How else can the number who capitulate be explained?’ The biologian’s artificial lungs wheeze as he speaks.

‘They need a live subject,’ adds Gallius. ‘He must be delivered alive, do you understand, sergeant?’

‘In order to verify our hypotheses,’ interrupts the biologian.

[...]

Later, the listener (a Raven Guard Sergeant) has some thoughts about this conversation.

What would make these men turn? I think. Some say that the tau are progressive, and their offers of equality and friendship are sincere. I am no fool. I do not believe as Biologian Tulk believes, and Inquisitor Gallius half believes, that there is some psychic or biochemical coercion at play. I doubt Tulk has seen much of the Imperium beyond the precincts of his own forge worlds. Gallius most certainly has, but men such as he are as preoccupied as the likes of Tulk; they see their task before them and so are blinded to the greater picture.

Context: In the aftermath of the Alpha Legion assassination attempt on him during the Horus Heresy, Guilliman is severely injured and is recovering. While he does so, he overhears the top officers of the Ultramarines Legion blaming each other for the assassination attempt coming so close to succeeding. Unable to take this anymore, he leaves his hospital bed and confronts them.

While we've seen Guilliman have debates and even arguments with Ultramarines before, this is the first time in the books where he is outright furious at his own sons. It shows what Guilliman values as a character. Its not the initial failure itself that is bothering him. It is the constant bickering the Ultramarines engage in instead of finding a solution.

The hatch of the apothecarion whirred open suddenly. A gust of environmentally stabilised air exhaled at them, like the opening of a void-lock. It stank of blood, of counter-septic gels, of graft cultures and sterilising solutions. The chamber revealed before them was gloomy, illuminated only by the low-light displays of life support systems. Guilliman had come to the door. He glared out at them like a wounded beast looking out of its cave-lair. He was breathing hard, and his torso, neck and one side of his face were wrapped in juvenat wadding and fixing wraps.

‘The walls,’ he wheezed, ‘are not so thick I cannot hear your bickering. This is not how we behave in crisis.’

‘Great lord,’ Auguston began. ‘You must recuperate and–’

‘This is not how we behave in crisis,’ Guilliman repeated. Dolor stepped forward and dropped to one knee, his head bowed. One by one, the others did the same, transhumans and humans alike. Auguston was the last to kneel.

‘How may we serve you, lord?’ Dolor asked.

‘Stand,’ Guilliman said. They stood.

‘I will take your private counsel now, tetrarch,’ Guilliman said. ‘I must do something more than just sit in a bed while I heal. First Master Auguston, you will carry out a full security review of the Residency and the city.’

‘Yes, my lord.’

‘I’m not looking for blame, Auguston, and I do not expect to hear of any punishment unless a true dereliction of duty can be proved. What I want to know is how they got in so we can prevent it happening again. Give us practical information, to improve our practical. Find out how else people come and go, especially the off-world influx. What needs to be monitored more closely? What procedures do we need to improve? Do any of the Alpha Legion – or any of our other enemies – remain among us?’

Auguston nodded. ‘My lord,’ he said, ‘I will have my staff officers detailed to this audit at once and–’

‘No, Auguston,’ said Guilliman. ‘You do it. Don’t hand it off. Oversee it personally. Consult by all means, but consult wisely. Bring in Polux.’

‘The Imperial Fist?’

‘Correct. The Fists were charged with the defence of Terra. Let us learn from their mouths about the performance of that duty. Am I understood?’

‘Yes, lord,’ replied Auguston, his jawline tight.

‘You think I demean you, somehow, Phratus?’ Guilliman asked. ‘You think I insult you by giving you a job that is beneath you? You are First Master of the Ultramarines, and that Legion knows no greater responsibility than the security of Macragge. I do not know how this task could possibly be beneath you.’

‘Apologies, my lord,’ said Auguston. ‘It is an honour. I will do this, and I will do it scrupulously.’

‘Of course you will,’ Guilliman said, nodding. ‘The rest of you return to your duties. Assist the First Master in any way he requires, and do your utmost to defuse any alarm or anxiety in the Legion, the Army and the public that has arisen because of this incident.’

[...]

He dismissed them, and turned back into the apothecarion with Dolor. Suddenly, as soon as the hatch shut, Guilliman reached out to the tetrarch for support. Dolor shouldered Guilliman’s weight without a word and guided him back to the bed. Shrouded medicae personnel, as silent as wraiths, lurking in the shadows, moved forward to reattach nutrient drips and monitors to Guilliman’s chest and limbs.

Small servitor units were moving around and beneath the bed, scrubbing away the bloodstains and incinerating dirty dressings.

‘She was right,’ Guilliman murmured as he lay back.

‘Lord?’

‘Euten,’ Guilliman said. ‘She advised against Auguston.’

‘I confess,’ said Dolor, ‘I’ve never liked the man, except when he’s been at my side in a fight. Then he has few equals.’

‘That is precisely why I chose him to succeed Gage,’ said Guilliman. ‘I was angry. Treacherous war had wounded us deeply. I wanted a warrior to lead the Legion to vengeance. But our situation grows ever more complicated, and Phratus is no politician.’

‘None of us are,’ said Dolor.

‘Not true. Not if I have done what I set out to do. I didn’t raise the Legion solely to build an Imperium and fight a crusade. Crusades are finite. Wars end. I raised the Legion to have a successive function in peacetime too – as leaders, as statesmen, as rulers of the Imperium once it was built.’

After previously defeating several Imperial Guard regiments in her career, Tau Commander Shadowsun went into the Tau 3rd Sphere Expansion with a rather low opinion of the Astra Militarum. However, as Tau forces pushed deeper into Imperial space, they start coming into contact with more elite Guard regiments like the Cadians and Catachans.

In the passages below, Shadowsun encounters the Catachan jungle fighters for the first time. At first she engages an armored convoy full of troop transports, dispatching it with ease as armored vehicles on a flat open terrain are easy targets for Tau Battlesuits and airpower.

However, her forces are later ambushed in the jungle by Colonel Iron Hand Straken and a large force of Catachans who remind her that the Imperial Guard are not to be taken lightly.

The yield capacitors of Shadowsun’s fusion blasters blipped gold. She dropped down from the flickering skies towards the column of boxy Imperial vehicles and triggered another full shot, twin beams of destructive energy spearing vertically downwards. She hit one of the lumpen things full on, an olive-hued tank that was little more than a mobile box filled with gue’la troopers. The transport exploded with a satisfying thump, and its passengers spilled out, grabbing for rebreathers or rolling out the fires that clung to their disgusting porcine flesh.

Yelling in defiance, the gunners in the cupolas of the other transports pivoted their pintle-mounted weapons towards the source of the killing shot. Shadowsun swung her hips back and her chest forward, her battlesuit smoothly boosting away from the chattering streams of slugs sent in her direction. Even a raw recruit could have avoided the ill-timed volley fired by the human soliders, and her Stealth cells made her all but invisible against the flickering clouds above.

Such poor warriors did not deserve to face the might of the XV104s. As if to prove her point, Drai’s team came alongside her, levelled their burst cannons, and tore apart the cupola gunners in a storm of blood and plasma. This really is too easy, thought Shadowsun.

There was little honour in shooting a fleeing foe, especially one as dull of wit as the Imperial Guard. Even their name was ridiculous.

[...several weeks later in the jungles of another planet...]

Shadowsun’s sensor suite flared the trajectory of another incoming barrage, but this time it came down behind her rearguard. Just as she was turning to survey the damage the treeline erupted into life. Hundreds of pale gue’la brutes roared out from the jungle in crude but effective camouflage, many of their number crying out praise to the Imperium’s dead god.

As the tau reeled in surprise, more and more of the gue’la emerged from the mists from either side of the road, their rifles spitting laser blasts into fire warriors and battlesuits alike. Some of them charged headlong at the fire warriors hunkered down at the side of the road, drawing knives the length of a tau’s arm and plunging them into the weak points of their armour. One in every ten of the gue’la emerging from the trees carried a cylindrical tank of the volatile liquid the Imperials loved to employ so much.

Cackling with alien glee, the gue’la troopers sent whooshing clouds of flame into the ranks of the tau firing back at them. Whole crowds of noble fire warriors were caught in the deadly clouds and transformed into burning, flailing puppets. One Imperial soldier caught a pulse rifle volley in the chest, its bolts slamming right through his torso and igniting the tanks on his back with a loud whooompf. The thick smoke of burning flesh mingled with the jungle mists, turning the ambush into a hellish confusion of half-glimpsed tableaus.

Shadowsun boosted up high, blasting columns of energy into the hollering gue’la troopers wherever a clear shot appeared.

‘Riptides, target the treelines! Heavy burst cannon only! Rearguard, move in to engage at close quarters! For the Greater Good, engage!’

[...]

Thick cylinders of plasma scythed down trees and gue’la warriors alike in a storm of indiscriminate violence. The blazing weapons systems panned back and forth across the treelines, reaping a madman’s toll on the gue’la platoons charging in. Here and there close-range las-fire picked at the Riptides to no more effect than light summer hail. Well-aimed krak grenades detonated against their joints, blackening paint but leaving the superstructure shining undamaged beneath.

The reactors that powered the battlesuits pulsed blue light into the mist as their rate of fire grew steadily higher. With a loud bang, something overloaded inside the Riptide closest to Shadowsun, a thin shriek coming from the battlesuit’s shuddering torso as it vented a geyser of steam. It was all the chance the gue’la needed.

They swarmed up the giant’s legs like arboreal simians, knives stabbing into the gaps between its armoured plates as their wiry fingers wedged into cracks. Shadowsun scythed past to cut two of them from the Riptide’s back with a precision blast of fusion fire. Oe-nu and Oe-hei hurtled after her, Oe-nu ramming bodily into a third and pitching him from the Riptide with a crack of broken bone.

Curving upright once more, Shadowsun glimpsed a scar-ravaged gue’la with a glowering bionic eye climb up high on the malfunctioning Riptide. He plunged a metallic arm deep into the battlesuit’s neck joint, rooting around before yanking half of a bloody tau head from the aperture he had torn in its metal hide.

Shadowsun’s stomach turned. She pivoted in midair in preparation to loose a blast right at the scarred gue’la, but the obscuring fog closed in around her once more, hiding him from sight.

A recent trend in Tau books is the growing role of humans in the Tau Empire. With the Tau recently taking more planets from the Imperium of Man, they are finding humans to be an increasingly reliable part of their armies.

Humans are not as good as the Kroot in melee and they can't really use the more advanced long range platforms like Battlesuits. However, they can use handheld Tau firearms (Pulse Rifles, Pulse Carbines, Rail Rifles etc.) and are generally physically stronger than a Tau. This makes them solid mid-range combatants who can keep the enemy occupied so that the Tau can use their heavy firepower without any interference.

This is highlighted by a human working with the Tau below during the Tau 3rd Sphere Expansion.

From "Broken Sword":

As we were mere gue’vesa, and not entirely to be trusted, we were assigned rear line duties, in our case guarding the site of this new settlement, named prosaically Mu’gulath’effu’ve – Mu’gulath First Bridgehead. Not very poetic, the earth caste. I can’t say I was completely disappointed.

[...]

There were a few fire warrior teams – real warriors, as far as the tau were concerned, but I’m not convinced. I know I’m on dangerous ground here, but I reckon you’ve enough to shoot me already in this recording should you decide I’m not sufficiently obedient.

I’ve noticed that when battle’s going against fire warriors, they’ve got less staying power than men. I’m looking forward to the time that we gue’la are trusted enough to take up front-line work with the likes of the mal’kor and the thraxians. We’ve a lot to give, not least flexibility.

Anyway, that’s something I’ve been badgering fire warrior command about whenever I’m able. I doubt I won them over, they must have judged the time right, because we will be shipping out to the front as soon as my vocal grafts take. I can’t wait, I really can’t. I can’t say all my messages and petitions did the job. But maybe what convinced them is partly down to what happened there, at Mu’gulath’effu’ve.

It seems that this individual got his wish as, after the 3rd Sphere expansion, humans are being regularly used as part of Tau base defense as shown below. They are placed on the outermost perimeter with the Kroot occupying nearby trees and hills as backup if the humans are overwhelmed in melee combat. The center is composed of Tau Fire Warrior Teams and Vehicles who hammer any potential attackers with railguns, drones and smart missiles while they are busy dealing with the humans/Kroot.

From "Elemental Council":

‘Looks like a very thorough implementation of chala’ol fortification theory,’ Ke said, her suit joints whining as she followed Swordlight.

‘Dirt-filled gabion walls, accreted reinforcement, Tidewall deployables. They mortared damaged ceramic alloy plates into the bunkers – see? I’ve only seen that with this coalition. Elevated watchtowers, a prefabricated drone hive. The motor pool doubles as a landing pad, that’s clever. If this is genuine chala’ol, the command centre should be… there, the dome by the living area, see? Excellent geometries. The outworks seemed well-designed, coming in.'

'Interesting what they do with the auxiliaries. Look.’

In the lush canopy overhead, Swordlight made out the unmistakable silhouettes of slouching human auxiliaries in low-density carapace, tarellian dog soldiers accompanying them, their canid legs and long snouts breathing truth into their name. The auxiliaries and mercenaries patrolled rope bridges, a handful of Tidewalls levitating silently around raised platforms to offset their exposure to enemy fire. Even higher, branches rustled, as if the untamed shadows within them feared the glow of the patrol base that bruised the forest’s darkness. A fitting metaphor for the noble T’au’va and the benighted cretins who resisted it, Swordlight thought.