In 1944, the Nazis deported Bloch to the Buchenwald concentration camp, as punishment for refusing to co-operate with their regime. He was tortured, beaten and held in solitary confinement. In the meantime, his wife was interned near Paris. Bloch was detained at Buchenwald until it was liberated on 11 April 1945. By the time of his return to Paris, he was crippled to such an extent that he could barely walk. He was advised by his doctors to settle his affairs, as they did not expect him to recover his health.