The UK Prime Minister, Tony Blair, is playing a passionate and prominent part in the Kosovo crisis.

He takes the hardest of hard lines against President Milosevic, makes the most specific promises to reverse the ethnic cleansing, and justifies Nato bombing as action in a just cause.

In domestic politics, Mr Blair is a risk taker whose risks have so far come off.

He led the Labour Party to election victory after 18 years, with a huge majority.

And in the British parliamentary system, he has untrammelled power at home that no other major western leader enjoys. He does not have to worry much about the opposition.

Clinton and Blair use similar rhetoric

US President Bill Clinton, on the other hand, always has to take the opinions of Congress into account.

President Chirac of France has to consider his Prime Minister, Lionel Jospin, a political rival.

And the German Chancellor, Gerhard Schröder, has to deal with a split within his junior coalition partner, the Green Party.

But this is only part of the story. Tony Blair is a practising Christian. Indeed, a regular column in a British satirical magazine Private Eye depicts him as an Anglican priest, the Vicar of St Albion's.

In speeches that seem to come from the heart, Mr Blair has taken the moral high ground and sounded a call to arms against barbarism - personified in the demonisation of Slobodan Milosevic.

He has proclaimed a crusade, albeit to save a Muslim dispossessed people.

Unparalleled passion

Other western politicians have sometimes spoken this way. Bill Clinton said Kosovo was a test of whether civilised nations awoke to the warning signs of evil before it was too late.

The new generation of German leaders - former left-wing radicals and green pacifists - have evoked parallels with the racism of the Nazis.

But no-one has spoken with the passionate intensity of Mr Blair.

Echoes of Margaret Thatcher

With the intensity goes a certainty that recalls Margaret Thatcher. Mr Blair makes specific commitments which most politicians would think rash.

He promises that Nato will remove all Serb forces from Kosovo and lead all the refugees back home. Our determination is absolute, he says.

Compare that with the vague undertaking of the American Secretary of State, Madeleine Albright, that Nato operations will continue until the crisis ends on just and durable terms.

Mr Blair's hostages to fortune may come back to haunt him; at any rate, people will remember them.

Argument over ground troops

It is the UK prime minister who is making the running in the debate over whether Nato should send ground troops into Kosovo.

He is careful not to get too far ahead of Mr Clinton.

In fact, it may suit Mr Clinton to have others take a more militant line at a tricky time for his presidency. He is busy watching American opinion polls, trying to decide which way to jump to secure a place in the history books which is not irrevocably tied to Monica Lewinsky.

This is not to suggest that Tony Blair, too, is not a politician to his fingertips.

He combines conviction with a detailed attention to public opinion and the use of focus groups, which owe a lot to Mr Clinton's example.

One criticism of both is that they are trying to run a war as if it were an election campaign - typified by the reluctance to call it a war at all.

Winning the media war

In Britain, Mr Blair's public idealism is backed up by an intensely professional information or propaganda machine - the choice of label depends on your point of view.

It is run by the man who is much more than his spokesman, Alastair Campbell.

After the damage to Nato's credibility caused by the mistaken bombing of refugee vehicles in Kosovo, Mr Campbell devoted some of his energy and talent trying to remedy the defects of the Nato media operation in Brussels.

The scrutiny of 24-hour television news has made the concentration on presentation, the rise of the spin doctors, inevitable.

Victory in the media war is seen as vital

Tony Blair is using the media machine to put across a moral message.

Unmarked by the long history of evasion which has tainted Bill Clinton, he now seems to be trying to build a consensus in favour of a ground operation in Kosovo which is increasingly seen as the only way to turn rhetoric into reality.

It has to be said that the stakes are higher for Mr Clinton and the task more difficult. Public opinion in America is more sensitive to military casualties than in Britain.