Amid the past week’s political sound and fury, one subject slid unnoticed under the platform. Britain is at war. Its soldiers are fighting and dying in two distant lands. Foreign policy, once the stuff of national debate, is consigned to cliché and platitude.

With casualties mounting in Iraq and Afghanistan, politicians dare not mention it, let alone disagree. The prime minister declared to his party conference in Bournemouth that “the message should go out to anyone facing persecution anywhere from Burma to Zimbabwe . . . we will not rest”. Britain will defend the oppressed anywhere in the world. Unfortunately Britain is doing nothing in Burma or Zimbabwe, while the message from Iraq and Afghanistan is that Britain chooses bad wars at America’s behest in which it gets beaten.

All the airbrushing in the world will not remove the greatest legacy that Tony Blair left his successors, that of “liberal interventionism”. Never articulated except in a confused speech in Chicago in 1999, it asserted Britain’s right to meddle in any country to which it took offence, under the rubric of “humanitarian just war”.

Nothing that Brown and his foreign secretary, David Miliband, said at their party conference indicated a change of direction. Nor did they say anything to which David Cameron and his shadow foreign secretary, William Hague, could risk taking exception. Blair’s wars, unprovoked by any threat to Britain, passed uncontested at the conferences, though the polls say they are highly unpopular.

In Brown’s case, Iraq has heavily qualified his core support within the Labour party. He went to Washington on taking office and received firm instructions not to quit Basra. Last week, in choosing to stay at the airbase (while pretending to “withdraw” troops), he disagreed with his generals and obeyed the White House. Brown has to engineer a retreat from Iraq to the beat of an American drum.

In Afghanistan British policy has detached itself from reality. Brown wants to “defeat the Taliban” and eradicate the poppy crop. He cannot do either. Indeed his supposed ally in Kabul, Hamid Karzai, is negotiating with the Taliban and has a government stuffed with drug lords.

For his part Cameron has been trapped into avoiding the government’s most vulnerable flank, its subservience to Washington. Only Brown’s opportunism in visiting Baghdad during the Tory conference brought the war into political focus. It remains unclear if the Tories wanted more or fewer troops in Basra. As for Afghanistan, Cameron said his “number one priority” was to “erase Taliban power”. This is the talk of a seaside drawing room.

None of Blair’s interventionist wars – Kosovo, Sierra Leone, Iraq and Afghanistan – has left a stable peace. Calm in the first two theatres still requires international military occupation. All have exposed equipment and manpower shortages in the army that Whitehall seems unable to meet.

Blair’s expansionism has only encouraged the distortion in British weapons procurement towards the air force and navy. Eurofighters are bought rather than army helicopters, aircraft carriers and Trident missiles rather than properly armoured vehicles. The price of these grandiose toys is paid not just by the taxpayer but by an underequipped army in battle.

Until 9/11 Blair could say with some justice that he was not dancing to the White House tune. His mentor in joining Operation Desert Fox (the 1998 bombing of Baghdad) and in Kosovo was his heroine, Margaret Thatcher. It was Blair who persuaded President Clinton to commit ground troops to Kosovo in 1999 and Blair who resumed the “white man’s burden” in recolonising Sierra Leone in 2000. When the proclaimed isolationist George Bush took office in 2001 Blair told his aides: “We’ve got to turn these people into internationalists.”

Only after 9/11 was Britain’s bluff called. Blair found himself dragged swirling in the slipstream not of America’s internationalism but its “retaliationism”. Blair’s humanitarian justification for war came to seem merely the baggage train of America’s ideological belligerence. As the political philosopher, John Gray, puts it in his book, Black Mass, the post-cold-war surge of interventionism appeared no more than “a combination of postimperial nostalgia with crackpot geopolitics”.

When even the Washington establishment began to distance itself from Iraq over the course of 2006, Blair remained adamant to the faith. Iraq failed to pass the tests of his Chicago speech: that war should be “prudent and achievable”, should see “the national interest truly engaged” and should have a nation “prepared for the long term”. The baffled head of the Foreign Office, Sir John Kerr, rightly asked: “Where does it end?”

A new tract, Just War, by Lord Guthrie, former chief of the defence staff, and Sir Michael Quinlan, former head of the defence ministry, repeats the question. Proportionality and the chances of a benign outcome are as vital to just wars as legality and good cause. Blair’s wars were justified only by his declaring them so.

The truth is that Britain can play the great power only when allied to America. There is no point in Brown boasting his determination to rescue a woman raped in Darfur or a monk tortured in Burma when he will not commit troops to either. Conditions in Zimbabwe or the Congo or Lebanon may be “unacceptable to Her Majesty’s Government”, but that phrase no longer makes dictators quake.

Blair’s doctrine of “hugging close” any and every incumbent of the White House has given British policy a dusting of glamour. But the next US administration is more likely to revert to George Bush in 2000, to never wanting “the 82nd Airborne walking the world’s kids to school”. Where then would be Cameron’s bombastic “security guarantees” to southern Iraq or his pledge to “erase” the Taliban? As Cameron admitted in an interview with my colleague Martin Ivens and then repeated in his conference speech: “You can’t drop democracy out of an aeroplane at 40,000ft.”

At least Brown has a sort of fallback position, his support for the new European constitution and its foreign policy apparatus. This supposedly offers the nations of Europe an alternative to dependence on America should they want, for whatever reason, to stop Serbs and Kosovans from clashing or to intervene in an African civil war or to police the ever-unstable Caucasus.

The miserable performance, both military and diplomatic, of the European Union over the past quarter century suggests that such a realignment of British foreign policy barely merits the name. But Cameron has not even the European option. Last week Hague derided the concept of an EU foreign policy shortly before demanding that “the EU systematically turn the screw” on Zimbabwe, whatever that means. This is not policy but attitude.

A Britain sailing the high seas with a couple of aircraft carriers, a lurking Trident and a squadron of overpriced Typhoons does not make a world power. It might conquer Sierra Leone but it could not contain any of the imaginable threats to Britain’s security, an aggressive Iran or a totalitarian Russia or even an African civil war.

Global influence can be exerted only by a global military power, and that today means America. What Washington wants must condition any foreign initiative, whether by individual states or by the European Union or by the United Nations. Britain has neither bases nor colonies. Big toys do not make small countries bigger.

If, as seems likely, America pulls in its horns over the next generation and Europe remains militarily inert, Blair’s Chicago speech is mere posturing. The same goes for liberal interventionism and rolling global regime change.

Brown’s new foreign minister, Lord Malloch-Brown, says: “Let’s not rely solely on America.” He talks of “doing exciting things with Sarkozy and Merkel”, yet does not specify those things. Under Blair the British government expended its hard-won capital of soft power – commercial, cultural and legal diplomacy – in favour of practising swordplay in the shadow of the Pentagon. This has led to bloodshed and disaster. But were that shadow to be withdrawn and were British soldiers still facing defeat in the deserts of Helmand, who then is to hold their hand, what lodestar is to guide them? Last week answer came there none.

simon.jenkins@sunday-times.co.uk

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