There were multiple causes of the war, including but not limited to, a potential sale of Luxembourg to France, the vacancy of the Spanish throne, and the Prime Minister of Prussia modifying and publishing an insulting telegram about a meeting of the French Ambassador. For whatever cause, a dangerously underprepared France declared war on Prussia (and thus the North German Confederation) in July of 1870. These circumstances led the South German states (Bavaria, Baden, Württemberg) to join the side of the North German Confederation.