Otto Hahn (1879-1968) was a German Chemist, who was awarded the Nobel Prize for Chemistry in 1944 – for his work in discovering Nuclear Fission. He was a distinguished Chemist who worked in the pioneering fields of radio chemistry. After the Second World War, he was a campaigner against the use of nuclear weapons and became an influential scientific figure in West Germany.
Otto Hahn was born in Frankfurt on 8th March, 1879. From an early age, he took an interest in Chemistry, and was supported by his prosperous parents. He studied chemistry at the University of Marburg and earned his doctorate in 1901. After a years military service, he worked as an assistant at the University of Marburg, before travelling to London, England.
He went to the University College, London and worked under Sir William Ramsay. Hahn hope to improve his knowledge of chemistry and English to help his professional career. In early 1906, he visited Montreal, where he spent a brief but fruitful time with Ernest Rutherford, where they investigated alpha-rays of radio actinium.
In 1906, he returned to Germany where he collaborated with Emil Fischer at the University of Berlin. With just a basic chemistry laboratory, Hahn discovered Meothorium, and the mother substance of radium, ionium. This discovery later had a great practical use for radiation treatment.
In 1907, he began a long working relationship with the Jewish Austrian physicist, Lise Meitner. They remained life-long friends though she later criticised him for not doing enough to oppose the Nazi regime and their persecution of Jews. Though Hahn did help a few Jewish scientists, and played a role in helping Meitner herself to escape to Sweden in 1938, after the Anschluss forced her to flee.
In 1910, he was appointed professor at the Kaiser Wilhelm Institute for Chemistry, where he became head of the radiochemistry department.
During the First World War, Hahn was conscripted into the German army and put to work on developing chemical warfare. He participated in developing and organising the use of poison gases, such as Chlorine and Mustard Gas on both the Western and Eastern fronts.
After the war, Hahn concentrated on the chemistry of radioactive elements. In 1921, with Lise Meitner, they made a very important discovery of Uranium Z – the first example of nuclear isomers. Although few paid much attention, this would prove very important in later nuclear physics.In 1936, he produced a book “Applied Radiochemistry” which became a very significant milestone in radiochemistry. 
During his time of internment, he was awarded the 1944 Nobel Prize for Chemistry ‘for his discovery of the fission of heavy atomic nuclei’ He was unable to attend because of his internment in England. Some scientists have argued his colleague Meitner should have been awarded the prize jointly.
Hahn was shocked to learn that the atomic bomb had been dropped on Japan in 1945, to devastating effect. He felt guilty that he, in some way, may have been responsible for this great loss of life.
After the Second World War, he campaigned against the use of Nuclear weapons, and in 1955 initiated the Mainau Declaration which warned of the dangers of atomic weapons. He became a leading figure within post war FDR, and was a high profile critic of rearming West Germany with atomic weapons. His opposition to the nuclear arms race caused him to be nominated for the Nobel Peace prize.
In 1966, he was awarded the Enrico Fermi Prize – the only time it has been awarded to a non-American.
Between 1948 to 1960, Hahn was the founding President of the Max Planck society for the advancement of science. Otto Hahn died in West Germany on 28th July, 1968.