Treaty of Frankfurt (1871)
|Treaty of Frankfurt|
|Created||10 May 1871|
|Location||Bismarck Stiftung und Archiv in Friederichsruh|
|Purpose||Ended the Franco-Prussian War|
The treaty did the following:
- Established the frontier between the French Third Republic and the German Empire, which involved the ceding of 1,694 villages and cities under French control to Germany in:
- Alsace: the French departments of Bas-Rhin and Haut-Rhin, except for the city of Belfort and its territory;
- Lorraine: the French department of Moselle, one-third of the department of Meurthe, including the cities of Château-Salins and Sarrebourg, and the arrondissements Saales and Schirmeck in the department of Vosges.
- Gave residents of the returned Alsace-Lorraine region until 1 October 1872 to decide between keeping their French nationality and emigrating, or remaining in the region and becoming German citizens.
- Set a framework for the withdrawal of German troops from certain areas.
- Regulated the payment of France's war indemnity of five billion francs (due within five years).
- Recognized the acceptance of William I of Prussia as German Emperor.
- Required military occupation in parts of France until the indemnity was paid (to the surprise of Germany, the French paid the indemnity quickly).
The treaty also established the terms for the following:
- The use of navigable waterways in connection to Alsace-Lorraine
- Trade between the two countries
- The return of prisoners of war
Factors that influenced the boundary 
The German military spoke up for control of the Alsace region, up to the Vosges (mountain range) and the area between Thionville (Diedenhofen) and Metz as a requirement for the protection of Germany. Most importantly, the German military regarded control of the route between Thionville and Metz as the most important area of control if there were ever to be a future war with France. 
Without a westward shift in the boundary the new empire's frontier with France would have been largely divided between the states of Baden and Bavaria, whose governments were less than enthusiastic with the prospect of having a vengeful France on their doorstep. It also would have necessitated the stationing of substantial Imperial forces within these states' borders, possibly compromising their ability to exercise the considerable autonomy the southern states were able to maintain in the unification treaty. A shift in the frontier alleviated these issues.
The new political border largely (though not entirely) followed the linguistic border. The fact that the majority of the population in the new Imperial Territory (Reichsland) territory spoke Germanic dialects allowed Berlin to justify the annexation on nationalistic grounds.
Natural resources in Alsace-Lorraine (iron-ore, and coal) do not appear to have played a role in Germany's fight for the areas annexed. Military annexation was the main stated goal along with unification of the German people. At the same time, France lost 1,447,000 hectares, 1,694 villages and 1,597,000 inhabitants. It also lost 20% of its mining and steel potential. The treaty of trade of 1862 with Prussia was not renewed but France granted Germany, for trade and navigation, a most-favoured nation clause. France would respect the clauses of the Treaty of Frankfurt in their entirety until 1914.
Citizenship Declarations 
In 1872, The German government told its new citizens that they must declare their choice to be either French, by the first of October, or German, by the same date of 1873. No declaration was necessary if one wanted to become German. If, however, one wanted to remain French, a declaration to that effect was to be made and they had to get out. Children were to have the same nationality as their parents chose. Those from the region who were overseas had to choose by October, 1873. Those who chose became known as the optants, the "choosers".
It resulted in mayhem with thousands of people boarding overcrowded trains to France. Many hoped to get around the law by leaving and then returning, crowding the trains going back. People were camping in the streets of Nancy. In Marseille, a charity was established to help pay the passage for any optants who wanted to emigrate to Algeria, where the colonial government gave them some of the best land. More than five thousand people took up the offer. In all, the total number of people in the region, in France, and worldwide who chose to remain French came to more than half a million. 
This treaty polarized French policy towards Germany for the next 40 years. The reconquest of Alsace-Lorraine, the "lost provinces", became an obsession characterized by a revanchism which would be one of the most powerful motives in France's involvement in World War I.
- Hawthorne, 217
- Hawthorne, 248
- Hartshorne, Richard (Jan, 1950). "The Franco-German Boundary of 1871", World Politics, pp. 209-250.
- Eckhardt, C.C. (May, 1918). "The Alsace-Lorraine Question", The Scientific Monthly, Vol. 6, No. 5, pp. 431-443.