Yep, you should expect war. So far, a lot of our other allies have disagreed to help us, but the UK is going to.
As for the people we are going against, none of us know exactly how "potentially evil" they are. It seems we just all have to wipe out all the powerful dictators with powerful weapons.
Will this war be the harbinger of peace? Nope. After we finish the war on this specific "ism" of terror, there will probably more war on some other concept globally impossible to go against. That's what I think at least.
There's no earthly way of knowing which direction we are going. There's no knowing where we're rowing or which way the river's flowing. Is it raining? Is it snowing? Is a hurricane a-blowing? Not a speck of light is showing, so the danger must be growing. Are the fires of hell a-glowing? Is the grisly reaper mowing? Yes, the danger must be growing 'cause the rowers keep on rowing, and they're certainly not showing any signs that they are slowing. AAAGGHHH!!!