Complex sentence: From May 1991 to December 1992, he served as the Additional Foreign Secretary/Deputy Foreign Minister supervising the work of the United Nations and Policy Planning Divisions besides acting as the Spokesman of the Foreign Office.
Split into simpler sentences: From May 1991 to December 1992, he served as the Additional Foreign Secretary/Deputy Foreign Minister. During this period, he supervised the work of the United Nations and Policy Planning Divisions of the Foreign Office besides acting as the Spokesman of the Foreign Office.