The realisation is sinking in. Europe needs to become able to defend itself without America’s help. From Friedrich Merz, Germany’s probable next chancellor, to Emmanuel Macron, the president of France and longtime advocate of “strategic autonomy”, politicians are calling for higher defence spending. The calls are welcome, indeed long overdue. The problem is that, so far, neither politician has offered much in the way of ideas on where the money for it is supposed to come from.