In May 1945, the usual approach by the TICOM was to force captured personnel to write "homework" describing processes used in a particular intelligence unit under interrogation, but this method was not fully developed.[8] The only document prepared as "homework" was one dated 6 August 1945 by Professor Dr Hans Rohrbach, along with several of his Pers Z S colleagues, which described the cryptanalysis of the American O-2 strip cypher, which was considered a most significant piece of work.[8][9]