The solution of the Rhineland question at the Paris Peace Conference of 1919 left no one happy. Here, in practical terms, lay the cornerstone of the whole diplomatic edifice. Could a peace fashioned through the compromise of fundamentally opposing views prevent Germany from breaking out on the world again or developing the ambition to do so?

Jacques Bainville touched on the nub of the difficulty in his disabused apothegm: the treaty appeared “too gentle for all that is in it which is harsh.” Notwithstanding the outcome on the battlefield, the disproportion between French and German power loomed almost as large as ever. France had suffered a demographic holocaust. Ten northeastern departments of the country lay devastated. By contrast, Germany retained the most technologically skilled population in Europe. Its formidable industrial resources remained intact. Could military dispositions provide satisfactory containment?

The French obtained a three-stage, fifteen-year occupation of the Rhineland. But that occupation would lose much of its value as a security guarantee when the Allies evacuated the Cologne zone five years after the treaty took effect. It would end at the latest in 1935, when the French faced their greatest manpower deficit and with the planned reparations schedule still only half fulfilled. The United States and Britain undertook in principle to come to France's aid in the event of a new attack.