Blair was advised by Clinton to get close to Bush and when US which was reeling from the 9/11 he offered wholehearted support as an ally. Following the US into Afghanistan and Iraq. This was a political decision Blair made as PM of the UK and it fitted in with his international policy of intervention.
However….he had to persuade the rest of the country and Parliament that this was the best course of action.
Blair used all of his considerable skills to manipulate the Parliamentary system. He knew he could not be blamed if he acted on the best advice of his intelligence services that there was a clear and present danger to UK interests and the advice of the government lawyers that the action was in their opinion legal.
So Blair made sure the record showed he got that advice. We had the ‘dodgy dossier’, a report compiled by the intelligence services based on the reports of a handful of spies they had in Iraq. This was enhanced and ‘sexed up’ to suggest Saddam had his finger on the trigger of missiles, weapons of mass destruction deployable in 45mins aimed at UK bases in Cyprus.
It was subsequently revealed after the invasion of Iraq that no such threat existed. It was fantasy.
He took a similar approach to the legality of the war and managed to change the legal opinion on the matter given the governments official legal advisor.
Blair later claimed he was surprised and astonished that the intelligence was quite wrong.
The US and the UK knew perfectly well who was responsible for 9/11 and Saddam had nothing to do with it. But the neo-cons in the US were looking for a major military campaign as an excuse to raid the US cookie jar and they had Bush in their pocket.
Blair was unfortunate. He was doing very well until 9/11 forced him down a very difficult path during which he pretty much sacrificed his principles for a political objective of maintaining the close alliance with the US.
If he had made a stand (as the French did) he would have had to suffer the strategic political consequences. The UK was ,and is still us, dependent, on the US for nuclear submarine missile systems. The alliance with the US in facing off continental threats dates from WW2 was crucial to victory. That alliance continued during the Cold War in the uneasy balance of power with the Soviets.
I can see why Blair did what he did. It was Realpolitik. Sometimes it throws a wild card and all your carefully laid out plans for improving your country are up in the air by sudden events happening overseas. You have to come up with a plan very quickly and stick to it. Sometimes that leads to very difficult decisions. Blair is judged very harshly, especially by the left wing of his party.
Blair was one of the most successful PMs. He and Brown can be credited with a lot of achievements. Unlike the subsequent Conservative governments who seem to have done little but squabble amongst themselves and lead the country over an economic cliff edge.
The UK and France pay top dollar to maintain a fleet of nuclear power stations and thereby the expertise to also handle nuclear defence.
Nukes are a trump card, an insurance policy. Ukraine gave them up and look what happened…They are, however, hideously expensive.