Why was the Sharingan's genjutsu ability not used much in the 4th Ninja War?

Question

Until the 4th ninja war, a Mangekyou Sharingan user had been showcased as a formidable enemy, with Genjutsu being one of their many powerful techniques. Itachi was adept with Tsukuyomi. Sasuke suppressed the Nine Tails' power with his Sharingan when Naruto faced him in Orochimaru's hideout.

It would be fair to consider that both Tobi and Madara are equally adept, if not better, with the Genjutsu abilities of the Mangekyou Sharingan. However, in the 4th Ninja War, they do not use Genjutsu much.

It could be argued that a Sharingan user may be able to cancel out Sharingan's Genjutsu, but Genjutsu could still be effective against a non-Sharingan user, such as Naruto or Bee.

Tobi could easily put them under Genjutsu and take over their tailed beasts, but he has not done it. He did not use it on Guy either when they fought.

Is there a reason why the Sharigan users did not use Genjutsu in the 4th Ninja War?

Answer 1

Using genjutsu on an enemy is futile, if they have allies nearby, who can infuse chakra to take them out of it. Genjutsu would not work on Bee, since his bijuu Gyuki would easily bring him out of it, as he did when Bee was momentarily trapped in Sasuke's genjutsu.

If Tobi were to use it on Naruto, Bee would easily bring him out of it. Moreover, during the Kazekage Rescue arc, Naruto already demonstrated that he knows how to cancel genjutsu (although it didn't work). Now he was much stronger, having learned Sage Mode and Bijuu Mode. In short, the chances of a Genjutsu on Naruto succeeding are very small.

Moreover, Tobi now had a Rinnegan, which he considered much more powerful, and wanted to try it out in battle, which he did with the so-called "Jinchuriki of Six Paths" technique.

As for Madara, his reincarnation did not go according to his plan. He wasn't meant to capture the tailed beasts, but even if he did, he did not have the Gedo Mazo to seal them in.

Further, ever since he had been reincarnated, Madara has spent more time showing off his powers, and complaining that the current generation of ninja is so weak compared to Hashirama and him than actually fighting. Casting a Genjutsu on "weak" ninja is probably not as satisfying for his pride as dropping meteors, using Mokuton techniques, Susanoo, and the like. :)

Answer 2

If you look at the wiki on how to combat a genjutsu, you can see the very first method which explains it:

The ninja needs to stop the flow of chakra in their body, and then apply an even stronger power to disrupt the flow of the caster's chakra; this is called Genjutsu Dissipation (幻術解, Genjutsu Kai). This can also be done by an unaffected ninja by applying a sudden surge of chakra into the affected person. In addition, tailed beasts can break their jinchūriki out of genjutsu in a similar fashion if they have a good enough cooperation, as seen in Killer B's case.

If you look at the bold part of it, you get your answer. Bee's relation with the Eight Tails is very good and thus, the Eight Tails will help him out anyways. In case of Naruto, we've seen the recent episodes, that he's formed a bond with Naruto and even otherwise, Kurama would have helped him out (like so many times before, as always).

As far as Kakashi is concerned, he's a highly skilled shinobi, with a Sharingan (and he has even activated the Mangekyo Sharingan), which, as you mentioned in your question, may cancel out each other. As for Guy is concerned, since another person can inject a chakra flow in your body to break the genjutsu, Kakashi could have helped out Guy in that case.

Answer 3

Well casting a genjutsu does depend on the ability of the enemy, if you recall Raikage was under a genjutsu when he fought Madara. But genjutsu against the likes of Madara and other Kage's would be futile. They are just too strong for anyone to cast a genjutsu on them. The level of the fights was high that's why even Itachi never used his Genjutsu yet he had to use Izanagi. One can get the idea why Genjutsu wasn't an option in this battle royal.

Answer 4

The argument of why Genjutsu was not used on Guy is an easy one to talk about. In short, guy was the perfect fighter against Genjutsu. He did not look at his enemies eyes nor hands while he fought, the two ways to activate the Genjutsu. He was arguably the most perfect fighter against the Uchiha. Naruto never once tries to evade Genjutsu and as he advances and builds a stronger relationship with his tailed beast, he doesn't have to. Plus, he was considerable chakra levels possibly surpassing all shinobi so canceling it becomes easier for him. Kakashi to be such a formidable user of the sharigan has proven to be the worst to stop it taking it head on. Obviously they do cancel each other out but one eye does not cancel two. This part is totally my opinion, but I do believe a Genjutsu takes a lot of effort. It is almost like a ceremony where the caster has to be extremely focussed. It's probably impossible to fight a fight while also keeping a person under your spell. Genjutsu is a good one on one tactic possibly one on two. But it's probably not best for more.