For modernity, but especially for France, the German prelude to war began in 1870 with the Franco-Prussian war. Any tale of the Franco-Prussian war must begin with German statesman Otto von Bismarck.
Bismarck saw the potential for a unified, industrialized Germany, and worked diligently towards that end. Not only a political genius but also iron-willed, Bismarck ultimately managed to weave together over 15 different territories, nations and states into a single unified Germany. A strong argument can be made that the Franco-Prussian War was mostly the result of another of Bismarck’s brilliant schemes.
Comparing the military strength and readiness of both Germany and France, Bismarck judged a war with France to be a low-risk venture, and managed to seduce French emperor Napoleon III into declaring war. Almost before the French army had completed its mobilization, German troops had won a smashing victory at the Battle of Sedan having killed, wounded or captured over 120,000 French soldiers. With Paris surrounded and the military on the verge of total collapse, the French surrendered, ceding an immense amount of reparations, including the province of Alsace and part of Lorraine.
Bismarck achieved all of his goals in this war: not only had he united the Prussian and Germanic princes against France in a new German empire, but that empire had even been expanded. Yet Bismarck, perhaps on account of his political and diplomatic brilliance, could not abide being given orders by the inept and immature emperor Kaiser Wilhelm II, whose reign began in 1888.
Over and over the two butted heads over foreign and domestic policy. The final break came in 1890 when Bismarck attempted persuade Wilhelm to leave politics alone on account of his incompetence. This culminated with a humiliating demonstration: Bismarck allowed Wilhelm to see a letter from Tsar Nicholas of Russia, wherein he described Wilhelm as a “badly brought-up boy.” Rather than accepting Bismarck’s comparative brilliance, Wilhem simply asserted his power, rescinding a 1851 Cabinet Order which effectively stripped Bismarck of most of his power. In this way, Wilhelm had essentially forced Bismarck’s resignation.
And so Germany, the most powerful nation in Europe, probably the entire world, passed to the hands of an incompetent and immature Wilhelm II, a man who considered himself not only a statesman superior to Bismarck, but also a brilliant leader (pandering to his inflated ego and wishing to avoid his criticism, German commanders would often allow the Kaiser to win at the war games during military maneuvers).
Bismarck was not the only one who judged the Kaiser like this. Most of the German political and military leaders were quite competent and talented in their own rites, but they universally recognized the need to tactfully keep Wilhelm from interfering. Indeed, the head of the German army (up to September 1914), Helmuth von Moltke, could not visit the front lines because he worried that if he left supreme headquarters the Kaiser would take over and mess things up.
Bismarck himself accurately summed up the results in a prophecy a few years before his death: “the crash will come twenty years after my departure if things go on like this.”
Incredibly, the Kaiser resigned almost twenty years to the day after Bismarck’s death in 1898.