What event made the Compromise of 1877 possible?

The Compromise of 1877 was an informal agreement between southern Democrats and allies of the Republican Rutherford Hayes to settle the result of the 1876 presidential election and marked the end of the Reconstruction era.

answer; i believe that the correct answer is (chronological order);

"germany's geographic location was an advantage when it was on the offensive in the war because it was situated next to an extremely wide river, the rhine, which was difficult for the allies to cross."