In this task, you're given a passage, further information available on a particular linked term from the statement, and an answer term. Your job is to generate a question that can use the information provided to obtain the given answer. You should use the information on both passage and link information to create the question. Note that the answer to the question should be exactly the given answer, and if the answer is none, the answer to the question shouldn't be obtainable from the passage or linked information.
Q: Passage: The government of the Electorate of Hesse (Kurhessen) had begun building the FrankfurtBebra railway from Bebra in North Hesse to Fulda, Hanau and Frankfurt before its annexation by Prussia after the Austro-Prussian War of 1866. The project was completed by the Prussian state railways on 15 December 1868. Until the opening of the line south of the Main, trains from Bebra to Frankfurt had to use the North Main line and the Frankfurt City Link Line. On 15 November 1873 the new line south of the Main between Hanau and Frankfurt via Sachsenhausen and Offenbach was opened, including South Station (opened as Bebraer Bahnhof, "Bebra line" station) and Offenbach Hauptbahnhof. The South Main line is still the most important rail link connecting Frankfurt with Leipzig, Berlin and Hamburg.
Link Information: The Austro-Prussian War or Seven Weeks' War Answer: 2
A:
How many months did the war that preceded the building of the Frankfurt-Bebra railway last?