User blog comment:IamJakuhoRaikoben/Chapter 455: Magnolia's Defensive Battle, Review./@comment-7418318-20151005063419/@comment-7418318-20151005090957

You seem to misunderstand what I was suggesting.

I'm not saying that the entire army is an illusion, just the reinforcements that haven't been seen yet.

Now for the reason there are two options for that.
 * 1) They are currently striking all over the continent, wiping out amries all over the place and thus pre-empting the entire continent's ability to ever fight back.
 * 2) We were lead to believe that Fairy Heart is freakin' powerful. If Zeref concentrated all his forces into one place he risks losing them all. So instead me might fake such a concentration when in truth the troops lurk nearby, hidden magically, ready to pounce the moment Fairy Heart wipes out the sacrificial army. Being willing and able to sacrifice an entire army and several Shields would be quite the statement of Alvarez' vast ressources and power.