<p>He did not use the bankai because he could not use it. </p>

<p>His bankai Zanka no Tachi absorbs the flames of his Ryujin Jakka into the katana blade. During the battle in fake Karakura town, Wonderweiss absorbed his flames. Later when the flames sealed inside Wonderweiss's body are about to explode, Yamamoto has to shield it with his own body, which left his own body in tatters. It is reasonable to assume that he was either in no position to activate his bankai, or the bankai would not be strong enough since he couldn't absorb enough flames. </p>

<p>If he had known Wonderweiss's abilities beforehand, he may have gone straight to his bankai from the start.</p>

CC BY-SA 3.0
2016-06-15T15:53:10.780Z
It can also be pointed out that his bankai would have had devastating effects in the human world.  He completely disabled Toshiro's powers who was quite the distance away just by releasing it, because it rendered even the water in the air useless to Toshiro. That may have held him back enough that he never really had to use it until he was stopping wonderweiss's explosion, and it was too late.
Ryan
CC BY-SA 3.0
2013-09-17T15:53:29.467Z
Humm I see, it really makes sense. I forgot about Wonderweiss's ability, Thanks!
Rikkin
CC BY-SA 3.0
2013-09-17T19:02:12.637Z
Zanka no Tachi relies on flames no matter how you cut it. Wonderweiss by design should have been able to absorb them. The only ambiguity is in how much Wonderweiss could handle, but there is not enough evidence to determine if he would be overwhelmed.
Daz C
CC BY-SA 3.0
2013-09-18T07:26:37.047Z
@DazC You are missing my point. I did not say that he didn't use bankai because of Wonderweiss's ability. He shikai is very strong by itself, and like most shinigami, he started by using it. It got absorbed by Wonderweiss, and at that point, there was no use in using bankai, because the flames were gone. When the flames exploded, he had to use himself as a shield, which caused a huge damage to his body. That's why I said it is "reasonable" to assume that he couldn't use his bankai in that situation. Either this, or one can shrug it off saying "Kubo didn't think of it", and move on. Your call.
Masked Man
CC BY-SA 3.0
2013-09-19T07:53:02.540Z
@Happy My point was from what was happening to Ryuujin Jakka's flames, using bankai would render the same results by technicality. Regardless of his damage; hence, why Genryuusai stopped using his zanpakuto (well before sacrificing himself in fact) was a tactical move to quickly deal with his situation. The logic is there. The ambiguity I mentioned was to obscure the possibility of whether or not Wonderweiss could be overpowered by Genryuusai's power. Plus, flames from Ryuujun Jakka are taken in bankai, but that doesn't make it necessary to achieve bankai (like starting out with it is OK).
Daz C
CC BY-SA 3.0
2013-09-17T13:40:30.027Z
2013-09-17T13:40:30.027Z
Masked Man
<p>During the Arrancar war saga in Bleach, Yamamoto fought against Aizen before the arrival of Ichigo. In the end of the fight he used a kidou that almost killed himself tying to defeat Aizen. If I remember, this kidou uses the body as a "fuel" for it to work. </p>

<p>Spoiler:</p>

<blockquote class="spoiler">
  <p> But in the new saga, he showed his bankai against Juha Bach. And it's
 very powerful.</p>
</blockquote>

<p><img src="https://i.sstatic.net/39rkC.png" alt="enter image description here"></p>

<p>He said that never used his full power, why didn't he use it against Aizen? If he underestimated him, why would he use that kidou that almost killed him and ended up losing the fight, instead of using his bankai?</p>

CC BY-SA 3.0
2013-09-16T19:13:37.957Z
I'm going to risk and say "for plot purposes" but perhaps someone here has a better answer.
Madara's Ghost
<bleach>
Did Yamamoto Genryuusai use all his power aganist Aizen?
# Did Yamamoto Genryuusai use all his power aganist Aizen?
Posted by: username_0 on 2013-09-16
During the Arrancar war saga in Bleach, Yamamoto fought against Aizen before the arrival of Ichigo. In the end of the fight he used a kidou that almost killed himself tying to defeat Aizen. If I remember, this kidou uses the body as a "fuel" for it to work.

Spoiler:

> But in the new saga, he showed his bankai against Juha Bach. And it's
> very powerful.

![enter image description here](https://i.sstatic.net/39rkC.png)

He said that never used his full power, why didn't he use it against Aizen? If he underestimated him, why would he use that kidou that almost killed him and ended up losing the fight, instead of using his bankai?
**Tags:** bleach
> **Comments:**
> **username_1**: I'm going to risk and say "for plot purposes" but perhaps someone here has a better answer.  
---
## 1 answers
### Answer by username_2 on 2013-09-17. Score: 3 | Accepted answer
He did not use the bankai because he could not use it.

His bankai Zanka no Tachi absorbs the flames of his Ryujin Jakka into the katana blade. During the battle in fake Karakura town, Wonderweiss absorbed his flames. Later when the flames sealed inside Wonderweiss's body are about to explode, Yamamoto has to shield it with his own body, which left his own body in tatters. It is reasonable to assume that he was either in no position to activate his bankai, or the bankai would not be strong enough since he couldn't absorb enough flames.

If he had known Wonderweiss's abilities beforehand, he may have gone straight to his bankai from the start.
> **Comments:**
> **username_0** (2013-09-17): Humm I see, it really makes sense. I forgot about Wonderweiss's ability, Thanks!  
> **username_4** (2013-09-17): Zanka no Tachi relies on flames no matter how you cut it. Wonderweiss by design should have been able to absorb them. The only ambiguity is in how much Wonderweiss could handle, but there is not enough evidence to determine if he would be overwhelmed.  
> **username_2** (2013-09-18): @DazC You are missing my point. I did not say that he didn't use bankai because of Wonderweiss's ability. He shikai is very strong by itself, and like most shinigami, he started by using it. It got absorbed by Wonderweiss, and at that point, there was no use in using bankai, because the flames were gone. When the flames exploded, he had to use himself as a shield, which caused a huge damage to his body. That's why I said it is "reasonable" to assume that he couldn't use his bankai in that situation. Either this, or one can shrug it off saying "Kubo didn't think of it", and move on. Your call.  
> **username_4** (2013-09-19): @Happy My point was from what was happening to Ryuujin Jakka's flames, using bankai would render the same results by technicality. Regardless of his damage; hence, why Genryuusai stopped using his zanpakuto (well before sacrificing himself in fact) was a tactical move to quickly deal with his situation. The logic is there. The ambiguity I mentioned was to obscure the possibility of whether or not Wonderweiss could be overpowered by Genryuusai's power. Plus, flames from Ryuujun Jakka are taken in bankai, but that doesn't make it necessary to achieve bankai (like starting out with it is OK).  
> **username_3** (2016-06-15): It can also be pointed out that his bankai would have had devastating effects in the human world.  He completely disabled Toshiro's powers who was quite the distance away just by releasing it, because it rendered even the water in the air useless to Toshiro. That may have held him back enough that he never really had to use it until he was stopping wonderweiss's explosion, and it was too late.  
---
