LONDON – During the Second World War, a future prime minister, Harold Macmillan, said America is “the new Roman empire and we Britons, like the Greeks of old, must teach them how to make it go.” How goes the tutoring of Rome by Athens?

We are in the fifth month of the Libyan intervention that Barack Obama’s administration said would involve “days, not weeks,” an undertaking about which Prime Minister David Cameron was much more enthusiastic than Obama, who rarely mentions it. The intervention resulted from Cameron’s and French President Nicolas Sarkozy’s sudden zest for waging humanitarian war.

Before its objective became regime change, the point was to prevent Moammar Gaddafi from inflicting a humanitarian disaster. Officials here speak of “a crime being committed within our reach.” But what is that reach?

After Gaddafi is deposed, as he probably will be, and after undetermined other nations have been deputed to police Libya’s postwar chaos, which surely there will be, moralists can answer this question: Did NATO’s operations – actually, those of a minority of NATO nations – really serve the humanitarian objective of economizing violence in Libya? And people here can then decide whether this was a sensible undertaking by a British government whose post-recession austerity budget, announced before the Libyan exercise in power projection, involves a mismatch between political ends and contracting military means.

“Britain,” said Cameron, “has punched above its weight in the world, and we should have no less ambition for our country in the decades to come.” He said this when announcing plans to slice military personnel by 10 percent and the army’s tanks and artillery by 40 percent, and the decommissioning of Britain’s only aircraft carrier capable of launching fixed-wing aircraft. Britain will have no carrier, an essential instrument of power projection, until 2020.

Britain remains a sceptered isle, but not the seat of Mars. So, what weight will Britain punch above?

In a recent lecture here, Max Hastings, a distinguished journalist and historian experienced with and affectionate toward America, called upon British leaders to understand “how little attention we command among most Americans,” who are no longer Eurocentric and have declining regard for British armed forces, which have “shrunk very small.”

In 2002, during preparations for the invasion of Iraq, the then head of the British army, returning from a Washington visit, told Hastings, “Mass matters – and we don’t have it.” Hastings notes that the U.S. Marine Corps’ air wing is larger than the Royal Air Force. Americans know that “if the British Army shrinks as scheduled after withdrawal from Afghanistan, we shall thereafter be able to deploy only a single brigade group of 7,000 to 8,000 men for sustained operations overseas.”

Which has implications for the “special relationship” – Hastings says this is now “a rather pathetic British conceit” – between Britain and America. “If,” he says, “we wish to play our traditional role abroad in pursuit of any perceived important Western foreign policy objective, to enjoy America’s confidence and share its secrets, we must own armed forces and intelligence assets capable of earning these things.”

NATO’s secretary-general, Anders Fogh Rasmussen, recently warned that “at the current pace of cuts,” it is hard to see how in the future “Europe could maintain enough military capabilities to sustain” military operations such as those under way in Libya.

Actually, Europe could not sustain them today; only U.S. munitions, intelligence, refueling and other assets keep the Libyan operations going.

Hastings says France is the only European nation with which Britain “can plan jointly for future war-fighting contingencies with a reasonable expectation of commitments being fulfilled”: “No responsible British government could today make an agreement whereby its European partners would become responsible for, say, airborne surveillance or unmanned drone combat capability in a future deployment, because the risk is far too great that on the day, and for whatever reasons, the others simply would not be there.”

Since the Cold War’s end, the combined GDP of NATO’s European members has grown 55 percent, yet their defense spending has declined almost 20 percent. Twenty years ago, those nations provided 33 percent of the alliance’s defense spending; today, they provide 21 percent. This is why Robert Gates, before resigning as U.S. defense secretary, warned that unless Europe’s disarmament is reversed, future U.S. leaders “may not consider the return on America’s investment in NATO worth the cost.” Born to counter the Soviet army on the plains of Northern Europe, NATO may be expiring in North Africa.

© 2011, Washington Post Writers Group