We could defeat ISIS, but Russia has to get in the way of us. ISIS isn't a country, so it would be a very tough war, which would result in millions death and virtually a destroyed middle east. Russia would try to declare war on us because we killed their troops, they support Syrian troops which are basically terrorists too. A war against ISIS would need to be a World War to defeat them. ISIS will eventually fall.
The World can defeat ISIS if there is a collective will among nations to do so. The Allies defeated Nazi Germany and Imperial Japan during WWII which were both much greater threats than faced today. Therefore, if the civilized World is willing to use the resources necessary to win a war against ISIS, then yes, ISIS can be defeated.
ISIS has been terrorizing the world, not just the US. This is a world problem and we can only defeat them if we put aside our differences and defeat the evil that threatens our very way of life. We may very be on the cusp of WWIII and if we are the only way we can defeat evil is by joining forces.
The world can defeat ISIS. The group can defeated if the rest of the world teams up to provide military and economic support. The group's method are terror, and it is difficult to maintain a group based on intimidation. By combining the world's resources, ISIS will be badly undermanned and underfunded.
In my opinion, It can be stopped not defeated. No one likes to lose and since ISIS is not a person but a group of people, the war will never stop. The only way to for them to stop is to make them get what they want or manipulate them somehow to lose their ideals. Which the answer as anybody can plainly see, is nowhere to be found. Either that or the government could care less about this. Let this spread so the population can think that they are actually putting in effort to stop the plague so their support from the citizens grow.
No matter what we do, who we send in, what information we collect, what bombs we throw, there is no way we can defeat ISIS. Even if we kill all the people currently in ISIS, another cell will pop up, and then when we defeat that one, another one will pop up. If we could defeat them, wouldn't we have done it by now?