When the Second World War broke out, Behar was back in the Netherlands. In 1940, Germany invaded and quickly defeated the Dutch military. Behar was interned but released because he was only 17, and joined the Dutch resistance as a courier. In 1942, he escaped from the Netherlands and travelled to Britain via Spain and Gibraltar, reaching London in January 1943. There, he was reunited with his mother and his sisters, who had fled at the start of the war. In 1943, his mother decided to change the family name from Behar to Blake.