May 10, 1871

Treaty of Frankfurt (1871)

France and Germany sign the definitive Treaty of Frankfurt

The frontier was traded piece for piece: France kept a larger Belfort, and Germany took a compensating adjustment west of Thionville.

Five plenipotentiaries at Frankfurt

Five plenipotentiaries signed the definitive peace treaty at Frankfurt am Main on 10 May 1871 for the French Republic and the German Empire: Bismarck and Harry von Arnim for Germany, and Jules Favre, Augustin Pouyer-Quertier and Marc-Eugène de Goulard for France.

The document converted the preliminary peace terms agreed at Versailles on 26 February into a definitive settlement, and revised the proposed border around Belfort and Thionville.

Not all of Alsace, not all of Lorraine

France ceded most of Alsace and part of Lorraine, not the entirety of both historical regions. Belfort and an enlarged surrounding area stayed French in exchange for the frontier adjustment favouring Germany west of Thionville.

More than 1.5 million French inhabitants were annexed with the ceded territory. Those who wished to remain French generally had to declare that choice and move their domicile by 1 October 1872, although they could keep real estate in the annexed land.

Money, prisoners, archives, railways

The indemnity was 5,000,000,000 francs. The final 3,000,000,000 were due by 2 March 1874 and carried 5% annual interest, and 325,000,000 was credited against the total for transferred Eastern Railway rights.

The treaty also regulated the staged withdrawal of German occupation forces, the repatriation of prisoners — 20,000 were directed to Lyon and then immediately to Algeria — commercial relations, transferred archives and war graves.

Signature did not settle it: ratifications were required within ten days, and the instruments were exchanged at Frankfurt on 20 May 1871.

Sources

Researched 24 Aug 2026 6 sources not yet audited

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What the sources leave uncertain

The signature date is secure and uses the same Gregorian calendar on both sides.
Sources sometimes say the treaty itself transferred 'Alsace-Lorraine,' but the territorial settlement largely confirmed the February preliminaries and involved most of Alsace plus a portion of Lorraine, with detailed exceptions and exchanges.
Active large-scale fighting had already ended under the January armistice; 10 May marks the definitive treaty, not the last battlefield action.