While Ichigo and others were just entered the Hueco Mundo, Quincies had already been invaded the Soul Society.
Just like how they invaded the Las Noches, there was death everywhere they arrived. Many regular Shinigamis have died from the attack. Not only regular Shinigamis even some Vice-Captain has been slain by Sternritters.
Sternritters were special soldiers of the Quincy kingdom named Wandenreich.
Sternritters were strong individuals, easily taking down many Lieutenant ranked Shinigamis. Not only that they were strong enough to defeat Captain ranked Shinigamis.
Because of that only threat to Sternritters was Captains of Gotei 13. But they had a device that can steal Bankai from Shinigami forcefully which made Shinigamis, dependant on Bankai to be at their fullest power, practically useless in the fight. And if we consider only Captain and Vice-Captain ranking Shinigamis, as well as a few Lieutenant ranking Shinigami, can use Bankai it would mean almost everyone who had Bankai get stolen their Bankai.
Sternritters not only steal Bankai, but they also make it their own was the real nightmare for Shinigamis.
Because of this few Captains died during the invasion. One of them was Captain-Commander Yamamoto Genryusai.
***
*A few hours ago.*
It was a peaceful day in the Soul Society. But all the Shinigamis were ready for the incoming battle as they got information that Wandenreich will be attacking the Soul Society.
Suddenly many blue pillars appeared out of nowhere.
Shinigamis didn't waste any time and sieged them.
Soon from these blue pillars, men in white clothes emerged and killing all the Shinigamis around.
One such Quincy was the same man who fought 2nd Espada Ulquiorra Cifer.
Indiscriminately massacring numerous lower-ranking Shinigami, who are unable to injure him, the man was intercepted by 6th Division Lieutenant Renji Abarai.
While the man was effortlessly blocking Renji's strikes bare-handed, they were interrupted by the arrival of the Sternritter who fought Yammy Llargo and 6th Division Captain Byakuya Kuchiki.
When the man's hand was severely cut by Byakuya, other berated him for allowing his Blut to be broken so easily.
Blut was an ability unique to Quincy and it works the same as Hierro of Arrancars.
Byakuya after severing tall Sternritters hand quickly knocked down the other.
After the masked man was neutralized, Byakuya activated his Bankai, Senbonzakura Kageyoshi, only for it to be stolen by tall Sternritter's medallion.
Wounding Byakuya in the ensuing battle, tall Sternritter asked Byakuya if he was aware of how, rather than being poisoned, he has been infected by fear.
Commending Byakuya's resilience in not dying instantly like most of his victims do, tall Sternritter explained the fear-inducing ability of his Spirit Weapon, which causes victims to doubt everything and lose control of all rational thought.
After receiving a blow to the chest, an uninjured man declared Byakuya's heart is already stricken by fear towards the Sternritter despite Byakuya's remarkable willpower.
Striking the motionless captain, the man described how, unlike fear which comes from reason, true fear is instinctive, and so cannot be escaped.
Evading Byakuya's subsequent assault, the man used and attacked with the stolen Senbonzakura Kageyoshi, causing Byakuya to fall amid a torrent of blood.
As Byakuya lies heavily injured, the man tells him it was obvious he could not win against his Bankai with only his Shikai.
When Renji attempted an ambush from behind, the man negated the strike with Blut Vene.
Moving to attack as well, Byakuya was overwhelmed by the blades of Senbonzakura Kageyoshi and was smashed into a wall, grievously wounding him.
When other man prevents an enraged Renji from activating his Bankai by attacking him, the tall man chastised him for not waiting, for they could have stolen it as well.
Kuchiki Byakuya has been defeated like this alongside Renji Abarai.
While this fight was occurring Captain of 10th Division Hitsugaya Toshiro encountered Sternritter I, the Iron, Cang Du.
Hitsugaya initiated the battle by using his Bankai, Daiguren Hyorinmaru only to get stolen by Cang Du's medallion.
After stealing the Bankai, Cang Du used it to fight against Hitsugaya and almost killed him if it wasn't for his ice vapored magically as well as retreat.
Sternritter E, the Explode, Bambietta Basterbine after arriving at the Soul Society was gleefully killing every Shinigami she met before getting stopped by Captain of 7th Division Sajin Komamura.
Komamura immediately used his Bankai Kokujo Tengen Myo just to get stolen as well.
The Sternritter K, BG9 encountered and stole Bankai of the Captain of 2nd Division Soi Fon,
While this was happening Captain-Commander encountered the Sternritter O, the Overkill, Driscoll Berci.
Yamamoto easily killed him and went to find the King of Wandenreich, Father of all Quincies, Yhwach.
Not long after he found Yhwach who just finished Zaraki Kenpachi alongside his most trusted aide the Sternritter B, the Balance, Jugram Haschwalth.
Yamamoto states he came to annihilate him and finish his job from 1000 years ago but was ambushed by 3 Sternritters.
These three consisted of the Sternritter who stole Bankai of Byakuya, F, the Fear, As Nodt. The Sternritter who fought 10th Espada, H, the Heat, Bazz-B. And lastly the Sternritter U, the Underbelly, NaNaNa Najahkoop.
Yamamoto effortlessly defeated them with a single swift attack from Ruijin Jakka.
Yhwach stated that they were fools for trying to meddle in his fight.
Noting Yamamoto's disappointed gaze, Yhwach was unsurprised when Yamamoto attacks, injuring Yhwach's forearm, and stated he never valued his own subordinates' lives, though his cruelty would end today, prompting Yhwach to state Yamamoto still allows himself to be consumed by anger, much like in the past, despite growing old.
Denying this, Yamamoto attacked him again.
Barely able to avoid Yamamoto's next attack, Yhwach manifested his Spirit Weapon.
When Yamamoto acknowledged this action, Yhwach noted Yamamoto appeared to be waiting for him to draw his blade.
Confirming this, Yamamoto said he did so in order to ensure he would destroy him entirely and activated his Bankai, Zanka no Tachi.
When Jugram Haschwalth questioned if the scorched blade Yamamoto wields is really a Bankai, Yhwach cautioned him to not underestimate it before detailing its ability to incinerate anything it cuts in an explosion of flame.
Noting Yhwach must have seen this Bankai 1000 years ago, Yamamoto asked him if he truly believes it will be the same as back then before stating Yhwach can take the next blow from Zanka no Tachi and find out if he really wants to discover if his Bankai is the same as it was 1000 years ago.
Evading Yamamoto's attacks, Yhwach wondered why no flames came forth from the blade when his cloak was cut and if the Bankai could really have changed in the past 1000 years.
Reaffirming there is no Zanpakuto with a Shikai and Bankai which are unrelated, Yhwach discerned the true danger lies in the point of the sword after seeing the rubble it touched was instantly obliterated.
Confirming Yhwach's suspicions to be true, Yamamoto explained the ability of Zanka no Tachi, Higashi and said not even his Blut Vene can defend against it.
Underwhelmed, Yhwach stated he simply has to cut him without touching the sword and attacked Yamamoto, only to express shock upon seeing his attack did nothing finding the top half of his own sword had been incinerated.
Telling Yhwach he is too naive and should listen when others talk, Yamamoto said there must be a "west" if there is an "east" before making Zanka no Tachi, Nishi visible.
As Royd realizes only Blut Vene has prevented him from being incinerated even at a distance, Yamamoto asked why he was just staring and stated Yhwach would be killed even if he ran.
Firing a Heilig Pfeil, which was easily repelled, and with his sword broken, Yhwach declared there is more to a Quincy's tactics than their cross and arrows.
Activating Kirchenlied: Sankt Zwinger, Yhwach stated it to be the Quincy's ultimate spell of protection and warned Yamamoto anyone who steps into its radius will be torn apart by the "light of God".
Unfazed, Yamamoto negated the spell by activating Zanka no Tachi, Minami.
Alarmed by the resulting horde of skeletal corpses, which were populated by the Quincy whom Yamamoto has previously slain, Yhwach denoted the irony of a Shinigami who can raise the dead and called Yamamoto a disgrace to his kind before leaping over the skeletons to attack Yamamoto directly.
Impeded by a towering pile of corpses, Yhwach was talked into taking a closer inspection of them at Yamamoto's behest.
Horrified, Yhwach recognized the burnt skulls of his deceased subordinates among those already in the heap.
As Yhwach's hesitation allowed the horde to engulf him, Yamamoto, backed away and taunted him for failing to seal his Bankai before explaining why Yhwach could not do so.
When Yhwach cries out at this provocation, Yamamoto said Yhwach must still have a human heart.
Asserting the skeletons were not sufficient to stop him, Yhwach began to strike down his former allies.
Claiming he can see Yhwach's tears, Yamamoto stated the bitterness he experiences now is incomparable to the hatred the fallen Shinigami had for him before unleashing Zanka no Tachi, Kita: Tenchi Kaijin, eradicating almost all of the torso and left arm of Yhwach.
With much of his torso and left arm eradicated, Yhwach who was fighting and lost to Yamamoto apologized to Yhwach for not being strong enough, making Yamamoto confused.
Suddenly real King of Wandenreich appeared standing in front of Royd who impersonated him and killed him.
Yhwach told Yamamoto he went to meet Aizen and recruit him but unfortunately, Aizen refused the proposal.
Yamamoto used his Bankai but unfortunately, it was stolen by real Yhwach.
Yhwach explained because of Yamamoto's immeasurable spiritual energy only he would be able to steal his Bankai, before calling his Spirit Weapon and put end to the life of Shigekuni Yamamoto Genryusai by cutting him in half.