This post is the latest installment of our “Monday Reflections” feature, in which a different Just Security editor examines the big stories from the previous week or looks ahead to key developments on the horizon.

The Chilcot report has sent shock waves through the British political establishment, which is still recovering from the unexpected Brexit vote. The report, everyone agrees, offers a devastating critique of former Prime Minister Tony Blair, who famously told then-President George W. Bush that he would be with him through “whatever.” But what has been less widely noticed is the equally disturbing insight the report offers into the national security lawyering in the UK and the US during the lead-in to the war.

One of the most remarkable documents in the published evidence is a more than 200-page transcript of Lord Peter Goldsmith’s testimony before the Committee. In it, he details his initial resistance to — and eventual acquiescence in — the view that the use of military force against Iraq could be legally justified.

That view has now been widely (though not universally) repudiated. Most of the international law submissions to the Chilcot Inquiry are highly critical of Lord Goldsmith’s conclusion that the 2003 invasion of Iraq was legal. (It is important to note, however, that the report itself does not reach a decision one way or the other — a decision that has itself come under scrutiny.) Elizabeth Wilmshurst, who resigned from the Foreign and Commonwealth Office legal adviser’s office in 2003 because she believed the Iraq war was unlawful, clearly feels vindicated: After the report’s release, she wrote that “from all this material there emerges a very widely but not universally held view that the intervention was indeed contrary to international law.”

But then who signed off on what is now widely regarded as an illegal war — and why? The transcript of Lord Goldsmith’s testimony helps us begin to answer this question. (The Inquiry’s findings, based in part on this testimony, appear in Section 5 of the report.) Along the way, it offers unparalleled insights into the pressures brought to bear on government lawyers working on national security matters. (These lessons, I might add, are still all-too relevant today.) Moreover, the testimony highlights a contrast between Lord Goldsmith’s agonizing evolution and the US lawyers’ apparently uncomplicated embrace of legal theories the British lawyers rejected as manifestly implausible. At a minimum, this testimony ought to cause Americans to take a step back to consider why US government lawyers fell into line behind legal arguments our closest allies considered non-starters.

The story begins with Lord Goldsmith’s preliminary view — which was that use of military force against Iraq would be illegal. When the use of military force was first proposed, Lord Goldsmith, who was then Attorney General, looked at whether there was a self-defense argument supporting intervention. He concluded that there was not: “There wasn’t the evidence of imminence of threat which would justify us in saying self-defence was a basis for force.” He also concluded that humanitarian intervention was not a proper basis for use of force in this case. (In addition to his testimony, the report includes this letter from Goldsmith to the Secretary of State for Defence in March 2002, in which he makes these two points.)

His attention turned, therefore, to the Security Council. Some had argued that it might be possible to revive Security Council resolutions from the 1990­–1991 Gulf War, but Goldsmith made clear that this was not an argument he could support. By Goldsmith’s account, his advice led Prime Minister Blair to persuade President Bush to go to the United Nations Security Council to seek a new resolution, which he did.

The resulting resolution, UN Security Council Resolution 1441, “decided” that Iraq was in material breach of its obligations under earlier resolutions and that Iraq “shall provide UNMOVIC and the IAEA immediate, unimpeded, unconditional, and unrestricted access” to suspected WMD facilities. But the resolution stopped short of promising military consequences. When Saddam Hussein failed to cooperate, the question then became whether a second resolution was necessary to authorize the use of military force in response, or whether Resolution 1441 itself “revived” the Security Council authorization to use force.

Goldsmith gave the Prime Minister his provisional legal opinion that a second resolution was, indeed, required. Though he never puts it this way, what followed appears to have been a concerted effort to get him to change his mind. He met with Sir Jeremy Greenstock, apparently at the behest of the Prime Minister’s office. Greenstock argued that the French, Russians, and Chinese had all tried to place in the resolution an “explicit provision that it would be for the Security Council to decide on the use of force.” But “they had lost” and that meant that a second resolution was unnecessary. (As Sir Roderic Lyne points out in his questioning of Goldsmith, the same could be said of the Americans — they sought clear language authorizing the use of force in case of continuing material breach by Iraq and failed to obtain it. As Lyne puts it, “in a sense, you could say that they [the Americans] had lost and knew they had lost.”)

Goldsmith notes in response that the proper interpretation of Resolution 1441 was not such a problem for the Americans because they had concluded they didn’t need Resolution 1441. They had concluded that there had been a material breach of an earlier Security Council resolution — 688 — and that was enough: “They could have walked away from 1441,” Goldsmith explained. Indeed, the Americans’ primary concern was that 1441 not be interpreted in a way that would limit authority they believed they already had.

Though Goldsmith probably did not know it at the time, the US had considered the legal case for war against Iraq in three memos by the Justice Department’s Office of Legal Counsel. The first, by Jay Bybee on October 23, 2002, gives two justifications for using military force in Iraq: implied or implicit UN Security Council authorization (through Resolution 688) and anticipatory self-defense — both arguments, Goldsmith’s testimony makes clear, the British lawyers had early on rejected as manifestly implausible (hence the backflips over the meaning of 1441). (Notably, US government lawyers subsequently primarily relied on and defended the second argument — pre-existing Security Council authorization.) A second opinion, signed by John Yoo on November 8, 2002, considered whether Resolution 1441 altered the legal authority to use military force against Iraq (concluding that it did not), and the third, also by Yoo, on December 7, 2002, addresses whether false declarations on WMDs by Iraq constituted further material breach that would permit the use of force under 1441.

Back to Goldsmith: Goldsmith makes clear that Sir Michael Wood, then the Foreign and Commonwealth Office legal adviser (the equivalent of the US State Department Legal Adviser), and Elizabeth Wilmshurst, his colleague in that office, had firmly concluded that 1441 required a second vote by the Security Council to authorize force. Goldsmith remained persuaded by this view through the end of January. On January 30, 2003, he wrote to Prime Minister Blair that “notwithstanding the additional arguments put to me since our last discussion, I remain of the view that the correct legal interpretation of Resolution 1441 is that it does not authorize the use of military force without a further determination by the Security Council.”

In a particularly telling exchange, Goldsmith recounts that Wood advised his client, Foreign Secretary Jack Straw, that a second resolution was required in order to authorize force. Straw responded, “I take note of your advice, but I do not accept it.” Goldsmith felt that Straw’s response was “a rebuke to … a senior legal adviser for expressing his or her view.” To his immense credit, Goldsmith wrote a remarkable letter to Straw emphasizing his view of the role of legal advisers: “It is important for the Government that its lawyers give advice which they honestly consider to be correct: that is what they are there for. … To do otherwise would undermine their function as a legal adviser in giving independent, objective and impartial advice. … [I]f a Government legal adviser genuinely believes that a course of action would be unlawful, then it is his or her right and duty to say so.”

So how, then, did Goldsmith come to see things Straw’s way? His turnaround appears to have been brought about by a visit to the United States. He testified that in February, he met with State Department Legal Adviser William Taft IV, Alberto Gonzales (then White House counsel), Condoleezza Rice, and several other senior officials in the State and Defense Departments. They were, he noted, “speaking with absolutely one voice on this issue.” The Americans were of the clear view that “‘we have a right to go without this resolution.’” What’s more, they firmly held to the position that 1441 allowed them to use force without a second resolution.

On February 12, 2003, the day after he returned to the UK, Goldsmith told a junior colleague that he now believed that a “reasonable case” could be made that Resolution 1441 revived the authorization to use force in Resolution 678. At the end of February, he met with the Prime Minister’s advisers in Downing Street and told them of his revised view that there was “a reasonable case that a second resolution was not necessary.” Goldsmith put this advice in writing on March 7, explaining that the safest legal course would be to secure a further resolution, but that a “reasonable case” could be made that legal authority existed under 1441 (a position he continues to defend in his testimony). In his testimony, he explains that his evolved legal position came about because he had been persuaded by “the combination of Sir Jeremy Greenstock, Jack Straw and what had happened in Washington.”

One can’t help but come away from reading this testimony with mixed emotions. On the one hand, Goldsmith clearly struggled to come to the right legal view — and he was unafraid to tell the Prime Minister and Foreign Secretary what they did not want to hear. On the other hand, he ultimately adopted what is today widely regarded as an incorrect reading of the relevant legal authorities. That decision, moreover, cleared the way for UK participation in the war.

One tantalizing aside in the testimony offers a clue as to how this could have happened — other than the immense pressure Goldsmith was clearly under to adopt a position policymakers favored. There is an exchange over whether a “reasonable legal case” (the standard Goldsmith applied in his revised view of 1441) is the proper standard for a government lawyer to apply when a decision to use military force hangs in the balance. At the inquiry’s behest, Goldsmith defines a “reasonable legal case.” It is, he explains, a case “you would be content to argue in court, if it came to it, with a reasonable prospect of success.” Sir Michael Wood, in his own testimony, says that the bar should instead be “a higher degree of legal certainty.” (And, indeed, after coming under pressure from the military and the Treasury Solicitor for a more definitive answer, Goldsmith later adopted a more clear cut position. But when he made his crucial turn, he did so applying the “reasonable legal case” standard.)

This difference in their approaches to the legal question may help explain the two lawyers’ different positions on whether Resolution 1441 could be used as a legal ground for UK participation in the Iraq war. It may also explain Goldsmith’s about face: After all, if he only needed to be persuaded that there was a reasonable legal case, then the bar was exceptionally — some might say dangerously — low. And that, in turn, may help us understand how the UK got itself into what most now agree was an illegal war.