Because of the top secret aspect of the project, only British-born scientists were considered. Even despite their early contributions, Peierls and Frisch were not allowed to participate in the MAUD Committee because, at a time of war, it was considered a security threat to have enemy aliens in charge of a sensitive project. In September 1940, the Technical Sub-Committee was formed, with Peierls and Frisch as members. However, Halban did not take his exclusion from the MAUD Committee in as good grace as Frisch and Peierls. In response, two new committees were created in March 1941 to replace the MAUD Committee and the Technical Sub-Committee called the MAUD Policy Committee and the MAUD Technical Committee. Unlike the original two committees, they had written terms of reference. The terms of reference of the MAUD Policy Committee were: