Bob Woodward, award winning journalist who along with Carl Bernstein exposed the Nixon administration criminal activities cover up called Watergate, poses the question in Plan of Attack of whether the United States could justify a unilateral (single instigator) war against Iraq and Saddam Hussein that violated the sovereignty of an independent nation. To find the answer to his question Woodward investigated the dynamics of the George W. Bush administration by examining records and tracking the behavior and statements of the administration's key personalities.
For instance, Woodward examined General Colin Powell's actions and statements, particularly in relation to Powell's disagreement with the decisions being made about the war and his attempt to dissuade Vice President Cheney from advocating the unilateral Iraq/Hussein war. He also investigated the link between Scowcroft and the elder Bush, since it appeared that Scowcroft's messages about the inadvisability of such a war were covert messages opposing said war that originated from the elder Bush and were intended for George W. Bush.
Woorward's intention was to provide an accurate and detailed account of why George W. Bush led the U.S. into an unprecedented preemptive war against Iraq with the aim of deposing its dictator, Saddam Hussein, notwithstanding that Iraq is a sovereign nation, such as the U.N. Charter upholds as inviolate. Woodward's conclusion and critical argument is that even though George W. Bush could not justify a war against Iraq according to the U.S. Congress and the U.N. Charter definition of a justifiable war, having no clear expectation of victory nor exit plan nor clear world mandate of accord, Bush was nonetheless determined to initiate war against Iraq and refused to allow any obstacle stand in his way.
You would argue/prove the critical argument of Plan of Attack, which arises from the question Woodward poses, by referencing the facts about Powell, Cheney, Scowcroft, the elder Bush, and George W. Bush as highlighted herein, along with other personalities examined in the book.