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The killing of James Foley by Isis caused an upsurge of international revulsion and condemnation with harsh words from the US defence secretary and others. But the Obama administration is trying hard not to be sucked into a war that could be more serious than the US invasion and occupation of Iraq between 2003 and 2011.

What Isis showed by Foley’s very public murder is that it will always raise the stakes in any confrontation with the US and anybody else. It trumped America’s reassuring portrayal of the recapture of Mosul Dam by the Kurds aided by US air strikes as a

sign that Isis could be defeated.

How much has really been changed by the US airstrikes? Possibly less than first appeared: one of Isis’s great strengths is that it can switch its military campaigns from Iraq to Syria and back again, and much that happens on the Syrian battlefields remains unreported. It helps Isis that the US, Britain and their Arab allies don’t know how to retreat without humiliation from their three-year attempt to bring down President Bashar al-Assad, Isis’s main opponent in Syria. The rest of the Syrian armed

opposition is retreating, disintegrating or changing sides.

In the long term the US and their allies may well develop a degree of mostly covert co-operation with the Assad government but it will probably be too late.

All the attention in the last two weeks has been focused on the Isis offensive against the Kurds and Yazidis. But over the same period there has been much heavier fighting in Syria than in Iraq, with Isis storming an important Syrian army base at Tabqa on Sunday, capturing much equipment including jet aircraft. This was not a walkover as in Sinjar, but a bloody battle with 346 Isis fighters and 170 government soldiers reportedly killed.

Isis is winning victories where it counts, capturing two other Syrian army bases near Tabqa and a fourth in Hasakah province. The bottom line is that Isis fighters are now driving westwards, threatening Hama and Aleppo. They are only 30 miles from the latter, and could well take over the rebel-held part of the city. Washington, London and their allies still cling to their bankrupt policy of vainly seeking to displace Assad as Isis advances on the ground.

Patrick Cockburn’s new book is The Jihadis Return: ISIS and the New Sunni Uprising,