Saddam Hussein was OK by you?
Firstly, You've never been a conservative.
Only liberals refer to the doctrine of preemptive war as "The Bush Doctrine." The Bush Doctrine is, as Charles Krauthammer will tell you, something else entirely.
The Bush Doctrine entails the spread of Democracy around the world. Learn it, live it, love it.
As far as preemption is concerned, an invasion of Nazi Germany to liberate Jews prior to Hitler's declaration of war on the United States would have been entirely appropriate within every Christian construct imaginable.
Saddam had already gassed Kurds and was firing on U.S. planes enforcing the No-Fly-Zone. Your ignorance is sky-high.