- The US government had decided, early-on, that it wanted to invade Iraq for purposes of 'regime change' -- removing Saddam Hussein. They intend to use the possibility of WMDs and the threat of terror as a backdrop.
- They wouldn't mind some help, so they ask the British.
- The UK informs the US that they'd be fine with regime change, but they need legal backing before they can do anything. Unlike the US, they're actually afraid of the consequences of a legally unjustified war. Iraq hasn't actually threatened anyone all that recently, and there's not enough evidence of an imminent threat.
- The solution involves the UN: the US will accuse Iraq of having weapons and use the UN to demand the re-entry of inspectors. It is expected that Iraq will continue to refuse, thereby providing a "last straw" -- the US and UK can claim they've given Iraq all the chances it needs.
- Iraq doesn't refuse the inspectors. They're allowed in, but are finding nothing.
- The US now has a problem. If the inspectors stay, and continue to find nothing, they won't have a reason to invade -- Iraq will be proven to be without WMDs, thus negating the principle case for war. If they do find weapons, then the inspectors are clearly at least finding some of what they're looking for, proving that inspections might be more effective than war.
- The US therefore only has one option left: cast doubt on the inspections, get the inspectors out, and invade. As long as inspections continue, the last-resort argument for war is useless.
- The US claims that Iraq is hiding weapons from the inspectors, and delivers an ultimatum: either weapons must be shown, or the inspection will be cancelled and the invasion will begin.
- Iraq is in a position to lose, regardless. Either it produces evidence of weapons, therefore proving it has been lying to the UN and at the same time proving that the US allegations were true, or if it has none, is unable to avoid the invasion. Iraq stalls, as I recall, with reams of paper.
- The US now has "proof" of Iraqi WMDs: they have refused to produce them and the inspectors have failed to find them. Therefore, we can conclude that Iraq has weapons and has been hiding them, insulting the UN.
- The US invades.
- When the US inspectors also fail to find evidence of WMDs, US intelligence agencies are blamed for the failure.
- It's quite possible the administration believed that regime change was in the best interest of the Iraqi people, but for some reason thought we, the people, wouldn't agree. Perhaps they thought they had to give us a false pretext to do the right thing. If so, I'm insulted.
- It's also possible the intelligence agencies really did fail, and the administration actually thought they'd find WMDs with which to prove their allegations were true. This doesn't negate the possibility that they had already intended to invade Iraq, it just makes it possible they thought their alternate justification would pan out in the end.
- Many other explanations are possible. This is one model, one possible explanation for what happened, based on an interpretation of an official but secret British government memo. As we've already discredited US intelligence, why not theirs too? Have a go at it.
Then again, as they say ... never attribute to malice, that which can be attributed to ...