 On 14 September 1955 , the Apostolic Vicariate of Dakar became an archdiocese , and Lefebvre thus became the first Metropolitan Archbishop of Dakar . Archbishop Lefebvre was the first and foremost advisor to Pius XII during the writing of the encyclical Fidei Donum ( 1957 ) , which instructed the clergy and laity on the missions in the Third World countries and called for more missionaries . 
