The Franco-Prussian War was an example of the pursuit of nationalism because it was essentially engineered by Bismarck to make Germany unification more likely.
Before the war, Germany had been moving towards unification, but there were still differences between the northern and southern parts of Germany. Bismarck, leading the North German Confederation, believed that a war with France would unite the two regions. He believed that if a war happened, the two regions would come together in a show of nationalistic solidarity. As it turned out, he was right.
So, this war was an example of the pursuit of nationalism because it happened largely because Bismarck wanted to unite Germany.