ALEXEI NAVALNY has been forced into a grim theater of the absurd, tormented by Russian President Vladimir Putin and the sprawling security state he commands. Mr. Navalny, Russia’s leading opposition voice and critic of the Putin kleptocracy, has been sentenced on phony charges to more than two years in a notorious prison 62 miles east of Moscow, where his health is deteriorating. His decision to go on a hunger strike is risky and should raise alarms far and wide.

“Why do prisoners go on hunger strikes?” Mr. Navalny asked in a message posted to his Instagram account. “This question only bothers those who have not been prisoners. On the outside it looks complicated. But from the inside it’s simple: you don’t have any other methods of struggle, so you go on hunger strike.” Mr. Navalny has complained recently of back pain and that his right leg has gone numb, and now the lack of sensation is creeping into his left leg. He has been unable to sleep because guards awaken him once an hour for eight hours during the night to document his presence in Penal Colony No. 2 in the town of Pokrov. He lost 17.6 pounds before the hunger strike. He has demanded the prison allow medical specialists to treat him but has been refused.

“Who’s lying on the bed, bald and with glasses, with a Bible in his hands?” Mr. Navalny wrote. “That’s me. With a Bible, because it’s the only book I’ve been able to get in three weeks. And on the bed (super scandalous rule violation) because I went on a hunger strike. Well, what am I supposed to do?” Mr. Navalny says the prison is ruled by a select few who lord over the others by fear. “This is the Vladimir region. The life of a convict is worth less than a pack of cigarettes.”

“So what can I do? I went on a hunger strike to demand that the law be enforced and that a visiting doctor be allowed to see me. So I lie down hungry, but so far with two legs.”

Mr. Putin’s security forces earlier tried to kill Mr. Navalny with a Cold War-era nerve agent, which Mr. Navalny survived. The hunger strike could wreck his health. Mr. Putin’s response? Russia’s state television channel RT dispatched a video crew with Maria Butina, who admitted to serving as an unregistered foreign agent in the United States and served 18 months in prison before her release in 2019. According to Mr. Navalny, in a posting on his Telegram channel, she declared that he was in the best and most comfortable prison. He berated her as a parasite and servant of the thieves — his frequent sobriquet for Mr. Putin and his cronies.

The hunger strike is a desperate signal from Mr. Navalny of a worsening plight. He should not be in prison, he should not be sick, and he must not be silenced like so many other critics of Mr. Putin who were felled by poisoned tea, bullets in the night or untreated ailments in prison.

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