Since the beginning of Russia’s invasion of Ukraine two months ago, the gap between conspiracy theory and state policy has closed to a vanishing point. Conspiratorial thinking has taken complete hold of the country, from top to bottom, and now seems to be the motivating force behind the Kremlin’s decisions. And Mr. Putin — who previously kept his distance from conspiracy theories, leaving their circulation to state media and second-rank politicians — is their chief promoter.

It is impossible to know what is inside Mr. Putin’s head, of course. But to judge from his bellicose and impassioned speeches before the invasion and since then, he may believe the conspiracy theories he repeats. Here are five of the most prevalent theories that the president has endorsed, with increasing fervor, over the past decade. Together, they tell a story of a regime disintegrating into a morass of misinformation, paranoia and mendacity, at a terrible cost to Ukraine and the rest of the world.