The biggest plan in defeating Voldemort is to hunt down and destroy all his Horcruxes, and a significant part of the last two books is spent doing this. Dumbledore, the most powerful wizard able to stand up against Voldemort, risks and sacrifices his life for it.
This is justified by Voldemort being immortal until all the Horcruxes are destroyed, so there is assumed to be no point in trying to kill him before that. But this justification doesn't make sense, for many reasons:
- if he is killed again (in an ambush, in a fight, or an assassination), even if he doesn't truly die, his body will be killed, and he will spend a lot of time in a weakened state. Last time it happened, his side collapsed completely as soon as he died, and he needed 14 years to come back (the first 10 years of that being in a complete state of helplessness). It would be much easier to hunt for the Horcruxes while Voldemort was a weakened disembodied spirit and his supporters hiding or in Azkaban, than doing the same while Voldemort is in power, in the control of the Ministry, and you have to be constantly on the run from his goons.
- what if not all Horcruxes are identified correctly? The identity of most of them were just educated guesses. If Voldemort was even just slightly smart, he would have created one out of a pebble and hidden it in a desert. Or made it out of something heavy and dropped it into a volcano to sink deep into the Earth's mantle.
- even if not all Horcruxes could be found and destroyed, there are many other ways of permanently stopping him. Stun him, grab the body, then Obliviate all his memories. Or, if you aren't too morally restrained, then Crucio him to complete insanity. Or transfigure him into a piece of rock and bury it deep underground. Or place him in Azkaban, where he cannot use magic. And do it as soon as possible, instead of waiting until his followers get more and more numerous and gather more and more political power.
Am I missing something which makes it logical to try to find and destroy all Horcruxes before any attempt is made to attack Voldemort directly?