It is very unlikely that Russia will change its support for President Bashar al-Assad of Syria, despite calls to do so from foreign ministers from the G7 nations gathered in Italy in the aftermath of the use of poison gas in Syria and the US missile strikes.

Russia owes its return to great power status in the eyes of much of the world to its military intervention in Syria and will not want to change its previous stance. Mr Assad’s forces, which are backed by Russia, Iran, Hezbollah and Shia militias from Iraq, are close to winning the civil war and it is doubtful if President Putin, even if he wanted to, could remove the Syrian leader from power.

Boris Johnson said that the chemical attack on Khan Sheikhoun on 4 April had “changed everything fundamentally”. But on the contrary the balance of power on the ground in Syria is very much as it was before, and it is improbable that US policy will really switch from giving priority to eliminating Isis and al-Qaeda.

A problem in getting rid of Mr Assad as Syrian leader – as advocated in the past by the US, Britain and France – is that there is no reason to suppose that it would end the war in Syria or modify the savagery with which it is fought. Mr Assad leads one side in a civil conflict that believes that it would be slaughtered or forced to flee if the other side won. It would fight on, with or without his presence.

The other important aspect of the Syrian crisis that remains unchanged by the chemical attack is that, if Mr Assad and his forces were defeated, then the beneficiaries would be the Salafi-jihadi opposition. Isis and al-Qaeda-linked groups dominate the armed resistance to the Assad government even more firmly than they did a year ago.

The Italian foreign minister Angelino Alfano was more cautious than Mr Johnson about getting rid of Mr Assad, saying that decision should be left up to the Syrians. “I have to say, the Libya experiment did not go well,” said Mr Alfano, referring to the aftermath of the killing of Muammar Gaddafi in 2011 after he was defeated by a Nato-backed opposition military campaign and the country collapsed into anarchy. “We are still paying the price."

A further difficulty facing any insistence by G7 states that there be a political “transition” in Syria is that Russia is not Mr Assad’s only foreign ally. Prior to Russian military intervention in Syria in 2015, Iran was Mr Assad’s most important foreign supporter, sending military advisers and leading an axis of Shia powers and movements who see victory in the Syrian war as crucial to their very existence. Before the fall in the price of oil in in 2014, the Iraqi government gave significant financial assistance to Damascus.

It is still unclear how far President Trump’s policy in Syria has really changed from what it was before the 59 cruise missiles were fired last week at a Syrian airbase near the central city of Homs. Until then, Mr Trump’s policy in Syria and Iraq was much the same as that pursued by President Obama and seemed to be reaching a successful conclusion.