Viewed from Washington, the Syrian crisis has been only partly about chemical weapons. The other crucial commodity at stake was American “credibility” – that mystical quality on which US and global security is often deemed to depend.

A Russian diplomatic initiative has saved Barack Obama from the prospect of a humiliating defeat in Congress over Syria. Yet the entire episode has left the impression that America’s president, politicians and public are increasingly reluctant to deploy military force – even when a US “red line” has been crossed. That has raised worries that America’s rivals, from Iran to China, will soon be tempted to test US resolve.

This possibility is certainly there. Yet those who worry that US power rests on the nation’s willingness always to enforce its red lines are taking too narrow a view of what “credibility” means for a great power. The willingness to honour security commitments is just one element. Not making terrible mistakes in foreign policy is another crucial part of credibility – as is the preservation of a strong economy and an attractive society. The biggest blows to US global power and prestige in the past decade were inflicted by the Iraq war and by the financial crisis of 2008. Neither had anything to do with an unwillingness to defend a red line or a reluctance to fire off cruise missiles.