What happens when you boil a frog? It doesn’t notice the warming water until it is too late. According to Margus Tsahkna, Estonia’s foreign minister, Russia is boiling Nato like a frog. He fears that Vladimir Putin’s provocations of Nato (none of which on their own would necessitate a military response) will become increasingly and slowly severe, testing and ultimately undermining Nato’s defences. There is force to his argument.

Two weeks ago, Polish air defences shot down Russian drones. Last Friday, Russian jets violated Estonian airspace and forced Nato planes to scramble. More drones, operated by a ‘capable actor’, according to a Danish Police spokesman, flew over Norwegian and Danish airports earlier this week, forcing their closure. This coincided with a cyber attack on Brussels and

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