FOR the family of Richard Phillips, the captain of the Maersk Alabama, his rescue by special forces was the best possible Easter present. For Americans it was an exhilarating display of American power, and for Barack Obama it was a gratifying demonstration that he isn`t the wimpish pacifist the Republicans called him.

But to a detached observer, this gung-ho adventure in the Indian Ocean is the rule-proving exception. What we have recently seen far more often is what a New York Times headline on the piracy story said last Thursday “US power has limit”. We`re dealing, that`s to say, with one of the most important discoveries of our time the impotence of great might.

Today there is only one hyperpower. The US is, on the face of it, mightier than any other imperial power in history. And imperial is the word it`s more than 50 years since Reinhold Niebuhr, the great American moral philosopher (and one of Obama`s favourite writers), wrote about the new age of American empire, “however frantically we deny it”.

By now it`s scarcely worth denying, frantically or otherwise. One evening last year I was idly channel-hopping through the sports programmes and lighted on the midsummer All-Star baseball game. There was a patriotic interlude, when the announcer said their thoughts were with the American servicemen and women “in the 153 countries where they are stationed”. That`s an impressive figure out of 192 member states of the UN.

American military spending is very much greater than the next 10 countries combined, friend or foe. Even now, 20 years after the Soviet Union began to crumble, the US air force and navy hold an immense number of nuclear warheads, weaponised and ready to go — but where? With all that might, the military operations in western Asia have turned out to be far more difficult than Washington originally envisaged. By the autumn it will be eight years since US forces entered Afghanistan, and it`s six since the invasion of Iraq. Even six years is longer than the combined length of American participation in the first and second world wars.

Although the Afghan campaign was originally more justifiable than Iraq (which isn`t saying much), it now looks less winnable. Even in Iraq, the vaunted success of the “surge” may prove deceptive if it persuades the Americans that they can win a permanent military victory there.

This is not as new as we might think. Go back to the heyday of the Cold War. The US and the Soviet Union each held a nuclear arsenal that could annihilate the other, or for that matter the whole world. But what happened? The Americans were humiliated in Vietnam by one rag-tag peasant army, and the Russians were humiliated in Afghanistan by another.

One could go back further than that. In a Dublin television studio three years ago we were discussing the legacy of the 1916 Easter rising, and something I said provoked a politician to shout, “We beat you in the war of independence” — the somewhat grandiloquent name for the troubles of 1919-21. Well, yes and no. In 1919 the British army was several million men strong and had just played a leading part in winning the greatest war then known.

The idea that it could have been defeated in conventional military terms by a few hundred gunmen (guerrillas or terrorists, according to taste) is demonstrably absurd. What the British were among the first to learn was the difficulty of subduing an irregular rising that enjoyed active or passive support among the local populace.

A hundred years ago, any one of half a dozen imperial powers could have conquered Somalia in a matter of weeks with a couple of gunboats and a few battalions.

Since 1993 and the bloody “Black Hawk down” fiasco in Mogadishu, the Americans have steered well clear of Somalia. They could nuke it flat, but that doesn`t quite meet the case. And that episode is instructive. The Americans were horrified by the loss of 18 of their men, but at least 1,000 Somalis were killed at the same time.

Nothing is more frightening to us than suicide bombing. It is indeed repugnant, but it also proves what the Roman philosopher Seneca said long ago “The man who is not afraid to die will always be your master.” That applies, above all, to prosperous, sybaritic, modern western societies, which no longer have any appetite for sacrifice and suffering. Is it any wonder we are mighty but weak at once?

— The Guardian, London