I don't get this.
Did Obito think that it would be easier to go to war with the whole shinobi world rather than capture the 8-tails and 9-tails Jinchuuriki on the low like how he did with the other ones? He basically ended up fighting not only both of them but also the entire shinobi world.
Would Obito's plans succeeded if he did not declare war and kept everything under the radar till the end? I believe he'd have been successful and that he wouldn't have needed to summon Madara at all.