Well, you see... when I said we were fighting against a couple people, really what I meant is that our opponents had unbelievable powers. We were not only up against a man-made created army of clones that were over a hundred thousand large, but also, they had resurrected some of the strongest shinobi of all time in an undead form using a technique called Edo Tensei...

The strongest of them all is Uchiha Madara, who was considered one of the strongest shinobi of all time, while he was alive...

[ It's actually far more complicated than that, but this is the jist of it. ]