Is it true that Otto Von Bismark's Annexation of Alsace-Lorraine in the later 1800's helped set the stage for World War One?
A-L's annexation definitely put the French on a collision course with the Germans. It would be like if Canada declared war on the US, and then the US quickly curbstomps Canada and takes British Colombia. A-L had been the northeast border of France for centuries, and was seen as French as Paris (although there was a huge population of Germans there).
This obviously was not the biggest cause of WW1, but it definitely was a large factor.