In the Second World War, what happened to ambassadors after their homeland declared war on the country in which they were based?
In theory, this scenario was covered by the Havana Convention of 1928, which regulated the rights and duties of diplomatic officers. On the declaration of war, diplomatic relations between the two countries would be frozen, and their respective consular staffs and their families would be given the time and means to return to their home countries. This, certainly, was the experience of the British ambassador to Berlin, Sir Nevile Henderson, who delivered Britain’s declaration of war to the Nazi leadership on 3 September 1939. In the days that followed, he and his staff were safely dispatched to Rotterdam in a sealed train. The experience of the then French ambassador to Berlin, Robert Coulondre, was similarly positive.
The process didn’t always go so smoothly. In some cases it was prudent for the ambassador to be tactically absent, as were both the Soviet and
German ambassadors to Poland in September 1939. Moreover, the Havana Convention was signed only by the American states, so was little more than advisory elsewhere. Consequently, when the German ambassador to the USSR, Count Fritz-Werner von der Schulenburg, announced his country’s invasion of the USSR in June 1941, he swiftly found himself imprisoned; he was released only in exchange for the Soviet ambassador to Berlin, Vladimir Dekanozov.
In short, until the Vienna Convention of 1961, there was no legally binding regulation governing the treatment of diplomats in the event of hostilities. Although ambassadors and their staffs might reasonably expect fair treatment, circumstances or mutual antagonisms could easily intervene.