Board Thread:Versus Debates/@comment-1018594-20150821001654/@comment-734582-20150823205841

GreatestSin wrote: there is still the high chance that he didnt use it because he needed to spare chakra for his fight with madara Danzo fought and deliberately extended the fight with Sasuke so he could land Koto on "madara". Danzo is probably the only shinobi in existence at that point, who knew the full threat of Madara. Not from legends or anything, he's old enough to have either heard of his power firsthand or have witnessed it himself. Danzo had the opportunity to defeat Sasuke easily when bound, but didn't because Koto wasn't ready. Once it was he was unable to get to "madara" and so chose his sealing jutsu for a shot at "Madara" over a surefire defeat of Sasuke.

Danzo lost because of the Madara name, and as Tsunade explained later, Madara's name is a pretty powerful thing to have. If Danzo had known it was Obito, he likely wouldnt have bothered extending the fight with Sasuke (an opponent he could defeat) to prevent having to fight "Madara" (An opponent that he couldn't defeat other than via Koto). He would've forced his sword through Sasuke's throat.