Ulf Reichstein-Markham is a recurring character from the Man-Kzin Wars series of books. Along with Buford Early and Chuut-Riit, Reichstein-Markham is both one of the few major recurring characters, and one of the few characters to have a large role in stories written by more than one author.
Reichstein-Markham was born on Wunderland in 2390, the son of a solar system Belter. Following the occupation of Wunderland by the Kzinti in the First Man-Kzin War, at the age of 18 he joined the "Free Wunderland Navy," what purported to be a resistance group but was little more than a band of space pirates occupying the Serpent Swarm (Alpha Centauri's asteroid belt). He was responsible for the capture of the United Nations spaceship Catskinner, whose crew later were responsible for the assassination of Chuut-Riit. He also came under the control of a Thrint who escaped its Slaver stasis field before being destroyed by the Catskinner AI.
By the time Wunderland was liberated in 2420, Reichstein-Markham had become an admiral, and then was chosen to be Minister of War for the free Wunderlander government. He finally died in the year 2443 after being selected to chair the Interworld Commission, an early form of pan-human government established after the peace treaty with the Kzin was signed. Prior to his death, he had used his position to give the secret of hyperdrive to the Kzin disguised as a diplomatic packet, in the hopes of creating a lasting peace of equality between the two races. Although he did not live to see it, Reichstein-Markham's treachery meant that, far from his intentions, the Kzin would grow strong enough to launch four additional wars of conquest against the human worlds.