Vladimir Putin is probably right. You won’t often find those words in a sentence, but with 224 passengers of an A321 flight dead in Sinai, the Russian president’s words carry a certain authority when the subject is Islamist terror.

Speaking at the G20 in Turkey, Mr Putin said he had provided members with intelligence “on the financing of different Islamic State (IS) units by private individuals. This money, as we have established, comes from 40 countries and there are some of the G20 members among them.”

Mr Putin could also have mentioned governments. He could have explained that with 30,000 fighters being paid around $500 a month, IS is ravenous for money, that it depends on states and international banking, that those “private individuals” are fronts. But no G20 leader, the guilty among them, is oblivious to these facts.

People who have never fought and will never fight are preparing us for war. It is not, of itself, irrational. Paris was proof, if any was needed, that a “Middle East conflict” will not be confined to its region. IS has allowed no choice. What remains to be decided is how we fight.

What we know, for a certainty, is that the usual “military solutions” will solve nothing. The lesson has been available since Vietnam, since an airforce general named Curtis LeMay was advocating bombing an enemy “into the Stone Age”. He further argued that “we should shove them back into the Stone Age with air power or naval power – not with ground forces”.

That was in 1965. In due course around seven million tons of bombs were dropped. The hellish Agent Orange was dropped. By the time the shooting stopped, 58,000 Americans, mostly of the inevitable ground forces, were dead. Estimates of total fatalities start at 1.45 million.

We already know the American-led Operation Inherent Resolve against IS in Iraq and Syria has had limited effect. Its commanders can offer video-game scorecards – 129 tanks “damaged/destroyed” – but no predictions of a successful conclusion. Thus the demands begin for “boots on ground”. In this logic, one failed strategy requires another.

So Barack Obama, too, is probably right. Speaking in Turkey, he asserted that despatching ground forces would be “a mistake”. Furthermore, America’s president explained: “We would see a repetition of what we’ve seen before." He did not need to name names. Those responsible for the Iraq debacle want to make amends for their last catastrophe. The president is in no mood to oblige.

That is probably why France has invoked European Union treaties governing collective defence rather than article five of Nato’s founding document. The US has no appetite for a ground war, therefore such a war will not happen. Instead, Mr Obama and Mr Putin have edged towards an understanding: Russia’s client, Syria’s Bashar al-Assad, will be spared while all attention turns to IS.

Then what? When shock and fury subside, when democracies have hobbled themselves a little more in the name of security, when bombing brings no rewards and ground troops have not materialised, what follows? The urge for “action” is understandable. Satisfying armchair generals and the military establishment is irrelevant.

Mr Putin went to the heart of it. If the world wants to strike at IS it needs to understand a fundamental truth: medieval barbarism depends on modern systems. To survive, IS needs the oil trade, the arms trade, and international banking. Striking at those might not thrill amateur wing commanders, but it might get the job done.

“I’ve shown our colleagues photos taken from space and from aircraft,” Mr Putin said in Turkey, “which clearly demonstrate the scale of the illegal trade in oil and petroleum products. The motorcade of refuelling vehicles stretched for dozens of kilometres, so that from a height of 4,000 to 5,000 meters they stretch beyond the horizon.”

To be fair, Operation Inherent Resolve has not ignored IS oil revenues. As of last Friday, commanders claimed to have hit 260 “oil infrastructure” targets. That, though, was from a total of 16,075 strikes. Equally, Mr Putin did not explain why the motorcade had gone unmolested, or why Bashar al-Assad has been doing oil deals with his IS enemy.

The west, like Russia, is not without expertise in the oil business. Our governments know a thing or two about the arms trade, and international banking. We spend an average of $11 million a day collectively on airstrikes, but obvious ways for attacking IS, murky or mundane, get little public attention. You could wonder about that.

IS smuggles a lot of oil. Where does it go and how? Who buys it? The answers are not secrets. Some oil is smuggled through the territory of the Kurdistan regional government, some through Turkey, Syria and Jordan.

IS is running a business and business is one thing the west supposedly understands. If we can contemplate vast military enterprises then intervention in the oil trade is feasible, especially where certain Middle East countries, supposedly allies yet homes to those “private individuals”, are concerned.

The same could be said of armaments. It is well-documented that IS looted vast amounts of equipment donated by the Americans to the Iraqis. Even that stockpile would not sustain 30,000 fighters for long. As CJ Chivers of the New York Times wrote in April, the terrorists occupy “the downstream position in a vast arms watershed, with tributaries extending to distant corners of the world”.

Work by Conflict Armament Research, part of the EU-funded iTrace Global Weapon Reporting System effort, has established IS is parasitic upon the arms trade. The Islamists have acquired cartridges from Russia and the US, guns from Belgium, anti-tank missiles from a multi-national called MBDA, assault rifles made in China and ammunition from Iran. Some equipment has been captured; much has been bought.

We know all about the arms trade. So do the French, the Americans, the Russians and the Chinese. If the world is serious about eradicating IS, if it seeks a target, the guns that do the killing would be a place to start. The money that pays for the guns, money raised from oil, antiquities, robbery, extortion and “taxation”, would be next on the list.

It is well-known, because it is obvious, that IS depends on banking. No one says that its routes into the system are easily disrupted. Similar efforts against the drugs trade have had scant success for decades. But the inaugural meeting of the Counter-ISIL Finance Group – with the Saudis as co-chairs, indeed – only took place in Rome in March. Belated would be one word.

IS stores and transfers funds in huge amounts. The interconnectedness of digitised financial systems is, in that sense, its strength and its weakness. Attacking that weakness might be a better bet, surely, than destroying 356 Humvees and assorted vehicles.

Oil, the arms trade and international banking: the targets are easily nominated. The trouble might be that for the politicians promising action, they sound very like the way of life we are supposed to be defending.