As an accomplished linguist, and in particular as a fluent speaker of the Russian language and expert on Russian affairs, he became during the second world war, after service in the Intelligence Corps in Egypt and the Military Mission in Moscow with the rank of major, second Secretary to the British Embassy in Moscow and personal interpreter to the Ambassador, Lord Inverchapel.
Arising from this he acted as interpreter to Mr Churchill and Mr Eden at the Moscow Conference in October, 1943; at the Teheran Conference in November, 1943; at the Moscow conference in October, 1944; and at the Yalta Conference in January, 1945. Mr Eden made a personal request to the bank for the services of Mr Birse at the Moscow Conference of 1944. He also acted as interpreter at the prolonged Armistice negotiations with the satellite countries in Moscow during September and October, 1944.
In April, 1945, he accompanied Mr. Eden to San Francisco, and in July he was in Potsdam, acting as interpreter to Mr Churchill, Mr Eden, Mr Attlee and Mr Bevin. All these duties were of a most exacting and arduous nature, involving sixteen hours a day, and often more, for days on end. For his services he received the C.B.E. from our ambassador on behalf of H.M. the King, and the Order of the Red Banner of Labour from the President of the U.S.S.R. [Martins Bank magazine]