Final answer:
Bush believed the world must act immediately due to Saddam Hussein's defiance, alleged connections with terrorists, and the pursuit of WMDs, framing the situation as an imminent threat justifying preemptive action.
Step-by-step explanation:
According to former President George W. Bush's rationale in his "Iraq, Denial and Deception" speech, the key reasons he believed the world must act immediately were manifold. Firstly, Saddam Hussein and his regime had shown defiance against international norms and expectations. Secondly, the administration claimed there were alleged, albeit unsubstantiated, connections between Saddam Hussein and terrorists. Lastly, and most urgently, there was the assertion that Saddam Hussein and his regime were pursuing the development of weapons of mass destruction (WMDs). These points collectively articulated an imminent threat justifying preemptive action.
Despite international inspections led by entities like the United Nations indicating otherwise, the possibility of Iraq harboring WMDs was mainstreamed as a central justification for invasion. This narrative was propelled despite caution from intelligence reports and key figures like Secretary of State Colin Powell. Additionally, the linking of Hussein with the September 11 attacks and the presentation of Iraq as part of an "axis of evil" served to underscore the Bush administration's case for a doctrine of preemption, shaping the contours of this decisive moment in history.