Given recent history, it would take an extraordinary event and set of circumstances to arise for military intervention by Britain in the Middle East to be considered an option. This country contributed to the wreckage of Libya and Iraq, which were mistakes entered into because our leaders entertained prophecies of exaggerated catastrophe. The argument over the risks of inaction being greater than the risks of action has surfaced again in Syria with a chemical gas attack, orchestrated by Bashar al-Assad, that left dead children foaming at the mouth. The slaughter of helpless civilians defines modern evil. The latest atrocity in Syria’s agonising civil war should stain our conscience. Mr Assad is a murderous tyrant and his continued rule in Syria is an affront to humanity. That the Assad regime is shielded by his backers in Moscow and Tehran for their own self-interest should garner contempt. These are all awful features of a war, characterised by numbing brutality, that is entering its seventh year.

What has changed is the focus on the use chemical weapons, of which the Syrian dictatorship claimed to have destroyed its stocks, but which have plainly been used to kill innocents, against the backdrop of the poisoning of a former Russian spy by a nerve agent in Salisbury. In the words of the UK ambassador to the United Nations, “there should be no more victims of chemical weapons attacks, whether they take place in the war zone of Syria or in an English country town”.

But it would be wrong to think that this should be enough for the UK to join Donald Trump in bombing Syrian airbases that are quickly repaired and in use within days. Making the stakes appear enormous is a form of self-hypnosis that renders those under its insidious spell unable to resist simplistic military solutions.

Mr Trump is another reason to be cautious. His presidency has not been burdened with ethical pretence, and it is hard to take seriously his sudden respect for human rights in international affairs. The president called out the “horrible attack” by “Animal Assad” but seemed distracted by an FBI raid on his lawyer’s office. No wonder he is confused: it was only last week that Mr Trump ordered his generals to arrange a rapid exit of the 2,000 US troops who have been advising anti-regime rebels. Britain would gain little from hitching our foreign policy responses in this most complex of conflicts to such a shameless and mercurial figure. The fact is that airstrikes or a barrage of missiles might have a demonstration effect, but they would not change the military balance on the ground. Nor would a single attack alter the outcome of the war.

Syria is a battleground between forces backed by foreign powers. It is Russian airpower, as well as Iranian-backed fighters, that have enabled the Assad regime to conduct its policy of terror and retake territory. The US-backed rebels have gained control over large parts of the country’s north-east, including valuable oil fields, after they scattered Islamic State. Meanwhile Turkey has expanded into Syria and also finds itself toe-to-toe with US-backed Kurdish groups. The dry tinder of regional conflict has burst into flame – most recently between Israel and Iran.

Britain should replace mindless confrontation with common sense and courage. It should keep the focus on saying that the reconstruction of Syria is contingent on Mr Assad’s departure and the ethnic cleansing being stopped. Ministers should expand humanitarian aid programmes in the region to help deal with refugees. Given that the public is moved by the plight of Syrian children, the government should allow more to come and live here safe from harm. Military action is never to be taken lightly. To make some headway in resolving the conundrum of the Syrian civil war there must an articulation of a clear strategy in public. This would allow the risks and benefits to be aired and a plan sanctioned by parliament. The stakes are too high for anything less.