The permanent Secretariat of the League of Nations was headed by a Secretary-General. The latter was assisted by one Deputy Secretary-General and three Under-Secretaries-General.
The Functions of the Secretary-General consisted in the preparation of the work of the League of Nations and the execution of its decisions.
The Secretary-General was responsible for the direction of the Secretariat, which was the executive organ of the League of Nations. The Secretary-General with the approval of the Council appointed and removed the staff of the Secretariat. The international officials of the Secretariat were under the Secretary-General's supervision and might not seek or receive instructions from any Government or other authority outside the Secretariat.
The Secretary-General was also responsible for the organization of the secretariat both of the Assembly and the Assembly Committees. He was responsible for helping the Assembly and the members of the committees and conferences, meeting under the auspices of the League of Nations, to arrive at decisions, which were in harmony with the aims of the League of Nations. It was his responsibility to ensure liaison and co-operation between the different organs of the League of Nations, and between these organs and Member and non-Member States. The Secretary-General also maintained close relations with the important political centers of the world.
The duties of the Secretary-General in respect of the maintenance of peace were mentioned in the Covenant. That is to say, in the event of war or a threat of war, the League of Nations was required to take any action that might be deemed wise and effectual to safeguard the peace of nations. In the case of any such emergency, the Secretary-General had forthwith, on the request of any Member of the League of Nations, to summon a meeting of the Council. The Secretary-General also made all necessary arrangements for the full investigation and consideration of any dispute arising between Members of the League of Nations and submitted to the Council by one of the parties. On the submission to the Council of a case or dispute, the Secretary-General immediately communicated with the interested parties, drawing their attention to the necessity of taking whatever steps might be necessary or useful to prevent anything occurring in their respective territories which might prejudice the examination or settlement of the question by the Council and requesting them in the name of the Council to forward their replies to him without delay for communication to the Council and to inform him of the steps which have been taken.
The three Secretaries-General that successively headed the League of Nations were Eric Drummond (1919-1933), Joseph Avenol (1933-1940) and Sean Lester (1940-1946). Although their working methods were different, none of them had one's own Administrative Section, named after the French word "cabinet". However, each of them had one's own secretariat and staff. This is what we called the "Office" of the Secretary-General.
The Deputy- and Under-Secretaries-General also had their own secretariat, depending on the periods, though it seems they were often merged into the Administrative Sections these higher civil servants were responsible for.
The first Secretary-General E. Drummond was named in the Annex to the Covenant. Thereafter the Secretary-General was appointed by the Council with the approval of the majority of the Assembly. In 1932, the Assembly decided that the Secretary-General and all officials of the rank of Director or above would have to solemnly declare, before the Council in public session, to exercise in all loyalty, discretion and conscience the functions entrusted to them. The Secretary-General was appointed for 10 years, the Deputy Secretaries-General for eight and the Under-Secretaries-General for seven years. The appointment of the Secretary-General might be renewed for three years, those of the Deputy Secretaries-General for five years and those of the Under-Secretaries-General for a further period of seven years.