LONDON -- "Speak softly and carry a big stick" -- that was the advice of ebullient U.S. President Theodore Roosevelt in the early part of the 20th century. It may still have some relevance today.

The kidnapping by the Iranian Revolutionary Guard of 15 British service personnel in the Shatt-al-Arab waters at the top end of the Persian Gulf raises once again the complex issue of how such situations should best be handled. Whether they are released promptly, which could be happening as these words appear, or whether they are going to be held for a prolonged period, the whole incident provides some important lessons for the modern-day resolution of international quarrels -- for which Roosevelt had such a concise answer a century or so ago.

First, his advice about speaking softly is probably more relevant than ever today in this world of globalized media coverage and instant information. Megaphone denunciations by either side were never going to get anywhere in this ugly incident, as British diplomats clearly realized at the outset. Only after a few days, and with the greatest reluctance, did they release the facts showing that the British sailors and marines were captured in Iraqi, not Iranians, waters -- a fact that was, of course, promptly disputed by the Iranians with counter-facts and assertions, and a hardening of positions all round.

So what about the big stick? In Roosevelt's day, and in the days of British imperial dominance, that would of course have meant a gunboat, followed by the might of the British Navy, and no doubt a battalion or two of soldiers and marines to bring the kidnappers to their senses.

But that was yesterday. Today blunt military force makes no sense because the world is such a tightknit network -- an onslaught against any part of it produces paroxysms throughout the global system.

The Iranians no doubt appreciated that from the start, reckoning that they could therefore proceed with impunity, discounting any direct British intervention or even direct intervention by the United Nations -- despite the fact that the captured personnel were actually operating under a U.N. mandate in their task of policing Persian Gulf waters.

In this calculation they proved sadly correct. All the U.N. Security Council could summon up, in face of an outright attack on 15 people carrying out U.N. duties, was a slap on the Iranian wrist that Tehran could safely ignore. So there was no big stick there.

While there may be no big stick in the old-fashioned sense, in the age of total information and data integration there are some new big sticks that require neither gunboats, nor megaphone protests nor U.N. resolutions, feeble or otherwise.

Just as Iran, by being an integral part of the world trading and oil supply system, has the power to cause global chaos (for instance, by mining the Straits of Hormuz and thus blocking 18 to 20 percent of the world's oil supplies, bringing both energy and financial markets to a state of crisis), so the reverse applies.

For example, cutting off Iranian access to the global financial system London, helped by New York and by the European capitals, could bring the Iranian economy to its knees.

Already American and British banks have been preventing the mullahs from collecting the revenues for their oil and gas in dollars, as part of the pressure on Iran to comply with international rules over civil nuclear development. It is only one small step to prevent them from selling in euros instead, or indeed selling their oil for any hard currency.

But financial networks are not the only ones that can be closed down. The Iranian leaders may talk about America as the Great Satan, and Britain as the smaller Satan. But it is on American technology that their aircraft depend; it is American, Japanese and a bit of Russian technology on which their communications and business systems depend; it is on spare parts and components from Western powers that their entire energy industry infrastructure depends; and it is on the European economies, of which Britain is one of the largest (after Germany) that Iran relies most heavily for its export markets.

In a dozen ways the oxygen that supplies a modernizing state like Iran can be turned off and its cities paralyzed. No need to talk about force, or "taking out" Iranian nuclear facilities or any other kind of "hard" retaliation. Soft-power retaliation can do the trick and produce the big-stick effect in a way that Roosevelt never dreamed of, and in a way that even today neither the Iranian high command, nor many analysts seem to appreciate. In effect, Iran can be closed down.

None of this invalidates the need to proceed in handling this incident, or similar ones if they should regrettably occur, with quiet and subtle exchanges (the soft voice) as far as possible, and as far as indignant public opinion allows. But it is a reminder that there are still big sticks in the armory of international affairs.

If the present incident brings that lesson home to all countries and governments tempted to flout international law and the rules of civilized global behavior, some positive benefit will have flowed from an ugly and dangerous crisis.