Jan Valtin was the alias of Richard Julius Hermann Krebs (December 17, 1905 - January 1, 1951), a German Communist and Soviet agent during the interwar period. He defected to the United States in 1938, and in 1940 (as Valtin) wrote his bestselling autobiography Out of the Night. He also wrote several novels.
Valtin became active in the Communist movement as a boy, when his father was involved in the naval mutiny that heralded the 1918 German revolution. In 1923 he saw action in the failed Communist uprising in Hamburg. Sometime after this he was recruited by the GPU, the foreign intelligence service of the Soviet Union, and forerunner to the KGB.
After joining the GPU he helped run various smuggling enterprises, and helped organize Communist cells in the crews of merchant ships. As a sailor he visited many countries and could speak a number of languages including fluent English. He spent three years in San Quentin State Prison in California for an assault carried out under GPU orders.
After the Nazis came to power in Germany he fled to Denmark, where the GPU headquarters had relocated. At this time he was a seasoned GPU operative but fell out of favor with the leadership.