Tony Blair made the first move. Minutes after the first plane struck the World Trade Centre on 11 September, he was the first world leader to express in public his horror and his sympathy for the US.
In those first bewildering, frightening hours and days, the Bush administration, normally so determined in its insularity, needed external support. Grieving for the dead and for a lost world, it wanted to feel that it was not alone. In those early days the relative military strengths of the US and Britain did not matter. President Bush welcomed the Prime Minister's early declaration of support and the two of them have talked regularly on the phone ever since, as well as meeting twice for longer discussions. This staunch, prompt support is central to the relationship between the two leaders.
Yet how much influence the Prime Minister has over the President is debatable. Some government insiders at Westminster make big claims about it. But it is now, six months on from 11 September, that Britain's views really count, in the unresolved debate over Iraq.
Since 1991, we have been Washington's most faithful, indeed sometimes only, ally in the crumbling strategy of "containment", backed by a strict sanctions regime. Britain's participation in an offensive against Saddam is the absolute bare minimum if Washington is to pretend that a "coalition" exists.
For all the overt acknowledgements of partnership, the relationship between the two leaders is subtler than the stereotypes. It has sometimes been caricatured in different ways, none of them entirely correct. In the UK, Mr Blair's diplomacy has been portrayed as a triumphant example of Britain punching above its weight, exercising a cautionary influence on the pugilistic instincts of the Bush administration. Or he is seen as the lackey, carrying out Mr Bush's instructions, acting almost as his spokesman around the world – influential only in the sense that he agrees with whatever President Bush says or does.
In fact it is at the margins where Mr Blair has a role. He has earned access to President Bush, an access which is unique among European leaders, and allows him to appeal to the plodding side of the Bush personality. In Washington the battle for the President's mind is furious. Mr Bush has hawks to one side of him and pragmatists to the other. On one level, his instincts are as gung-ho as the hawks'. Mr Bush would have Saddam Hussein for breakfast before moving on to Iran for lunch. But there is another side to the President. He is a meticulous planner, something of a plodder, not as reckless in domestic and foreign policy as he is sometimes portrayed.
Leading the charge for immediate intervention is a coterie of conservative civilians, led by Paul Wolfowitz, the Deputy Defence Secretary and Richard Perle, head of an influential Pentagon advisory board. Their champion in the innermost counsels of the administration is the Vice-President, Dick Cheney. Get into Iraq, this school believes, and the rest will fall into place.
The State Department and the CIA are anything but convinced. What about the consequences on the region, asks the former; what guarantee is there that a successor regime will be any less wedded to weapons of mass destruction? And, say the spooks, a credible internal opposition does not exist – nor does the foreign-based Iraqi National Congress represent a credible external one. Finally, as always, the military commanders who will have to do the fighting and sustain the casualties are wary.
For all his demonisation of the "axis of evil", the President himself is uncertain. The Afghan campaign, as current events show, is not over, while the Palestinian-Israeli conflict is escalating to a point where it could upset every calculation over Iraq.
Mr Blair can fuel the Bush side that plods, or at least is cautiously gung-ho. A timeline of sorts is apparent. By mid-April, after his Texas summit with the Prime Minister, Mr Bush wants to see a firm plan for "regime change" in Baghdad. By June, a likely showdown with Saddam over the return of the weapons inspectors will be looming. Assuming Saddam continues to obstruct and procrastinate, the weather in the Gulf by late autumn would be cool enough – and a troop build-up might be far enough advanced – for an operation to start before the end of the year. The wagon of war may trundle more slowly than most people think.
Mr Blair's position is also complex. In speaking out against Iraq, as he has done recently, he is not merely echoing the thoughts of President Bush. For some time Mr Blair has been so convinced of Saddam's capacity to build up weapons of mass destruction that he is willing to contemplate support for military action. His concerns are that such action – if it is necessary – is not rushed and is carried out with as much international support as possible.
Whether Mr Blair holds much sway will depend entirely on the dynamics of the Bush administration. Already Britain's relationship with the US government, as distinct from that between the two leaders, is strained. The US Defence Secretary, Donald Rumsfeld, is so hawkish that he has no time for dialogue with the Ministry of Defence. He looks at Britain's puny military contribution and scoffs.
Mr Blair's relationship with President Bush cannot be as strong as the one he enjoyed with Bill Clinton in which two leaders built a relationship around a similar political outlook, fuelled by genuine mutual admiration. But Mr Blair is determined to cling to this current relationship. Almost certainly he has less influence than he imagines, but the Downing Street line is unswerving: better some influence than none at all.Reuse content