The nations of the EU must stop their collective decline as a military power. For years, this plea has been sounded by Nato chiefs and senior US officials who complain that European governments are slashing defence budgets far too fast in response to the economic crisis.

The recent intervention in Ukraine by Vladimir Putin, the Russian prime minister, has now given those fears even greater resonance. Russia’s effective annexation of Crimea has all the makings of a grand strategic moment for the EU, whose governments need to reflect on whether they can continue cutting military capabilities without fearing the consequences.

There are two reasons why European defence has become such a fraught subject in recent years. First, while the US remains the senior partner in the western alliance, it is increasingly focusing on the strategic challenge from a resurgent China. Japan and South Korea look to Washington to boost security guarantees against Chinese might. With Pentagon spending also being squeezed, this means the US is stretched.