The people who prepare President Barack Obama’s national security briefing must be wondering what to put at the top of the pile. Should it be the Russian assault on Ukraine, or the advance of the Islamic State of Iraq and the Levant (known as Isis) in Iraq and Syria? And what items should go just below that?

The violent anarchy in Libya, the dangerous stalemate in Afghanistan, the looming political crisis in Hong Kong, or a confrontation between Chinese and US planes, near Hainan island?

The US president might reasonably ask why all these crises are breaking out at the same time. His critics have a ready answer. They argue that the Obama administration has shown itself to be weak and indecisive. As a result, America’s adversaries are testing its limits and the US-led security order is under challenge in Europe, the Middle East and Asia.