After the defeat in the Franco-Prussian War, France had been humiliated, forced to pay an indemnity of five billion francs and lost the provinces of Alsace and Lorraine to the new German Empire, so as to permanently put France on the defensive. Though the French did indeed build an extensive amount of fortifications along their border with Germany, after 30 years plans turned offensive, thanks in no small part to Ferdinand Foch. France had a population and birth rate smaller than those of Germany and invented the concept of "élan vital" and decided on a strategy of "offensive to the limit", making the will to fight the cornerstone of French military planning. Colonel Louis Loyzeau de Grandmaison, took up Foch's doctrine and delivered two speeches before the École Militaire that set the foundations of Plan XVII, which was formally adopted in May 1913. French strategists took account of the possibility of envelopment by the German right and calculated that the more powerful the German right, the weaker the center and left would be. The French decided to concentrate their forces on the Rhine, planning to break the German left and center on either side of Metz, to cut off the German right and defeat the German armies in detail.