Why Putin will use nuclear weapons

However you try to spin it, the drone strikes that struck Moscow’s wealthiest neighbourhoods on Tuesday night represented a grim turning point in Putin’s flagging campaign against Ukraine. The surprise attacks — which killed eight people, and for which Kyiv has denied all responsibility — were the first against Russian civilians since the war began. They were also the most significant incursion into Russian territory since the Second World War.

Putin was quick to brand the strikes a “terrorist” act, while a rattled Yevgeny Prigozhin, head of the Wagner mercenaries, gave war chiefs a...