When German forces invaded and occupied Denmark on 9 April 1940, the Danish krone was used in the Faroes. However, all exchange between the Faroes and Denmark halted as a result of the occupation, leaving one currency to develop in two markets independently of each other. On 31 May 1940, special Faroese banknotes were introduced. They consisted of Danish notes with a special stamp. These notes replaced unstamped Danish at par.