Even Berlin and Brussels are bending fiscal rules in the face of Russia’s threat. Will the chancellor still stick to hers?

As the Nobel laureate Robert Lucas quipped during the 2008 financial crisis: “I guess everyone is a Keynesian in a foxhole.” Donald Trump’s upending of the postwar security consensus has underlined the enduring wisdom of Lucas’s observation. But now, instead of bank bailouts and emergency bond buying, European firepower is being directed at bombs, tanks and drones in the desperate fight to secure the continent’s border with Russia.

Berlin and Brussels – typically capitals of financial orthodoxy – have been convinced that this approach is required once again. Under the plan put forward by Germany’s chancellor-in-waiting, Friedrich Merz, Berlin is on the brink of relaxing its “debt brake” rule to pave the way for spending on defence and infrastructure worth an additional €1tn (£840bn) over the coming decade.