Franco-Prussian War

The Franco-Prussian War - known in Germany as the German-French War (Deutsch-Französischer Krieg) and in France as the Franco-German War (Guerre franco-allemande) or "Guerre franco-prussienne" - was the last of three wars that led to the unification of Germany (the first since the Holy Roman Empire had any political power).

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.

The result was a 10-month Curb Stomp Battle as the Prussians decimated the French in all but three battles (where the French won one at Broney-Colombey and fought to a draw in two others), captured the French Emperor, Napoleon III, and unified Germany.

Another result of the war was Germany's annexation of Elsaß-Lothringen (Alsace-Lorraine), which they held until World War I. Moreover, the French had to leave Rome, indirectly finishing the Unification of Italy.

The defeat of Napoleon III led to his fall and the proclamation of the Third French Republic, which continued the war longer than the Germans expected by continually raising new armies even as Paris was besieged. In a bloody epilogue after the signing of the definitive peace treaty French fought French as the forces of the conservative central government put down the Paris Commune, a short-lived revolutionary government which was in control by revolutionary members of the French working class. While short-lived and petty by that time, it would later on inspire a man named Vladimir Lenin to start the October Revolution and create Soviet Union, thus being responsible of communism's first steps as a major power through the 20th century.

Franco-Prussian War provides examples of the following tropes:

Balance of Power: One of the wars that indirectly led to the basis of the Alliance system and thus, World War I (which led to the Great Depression, which led to World War II, which led to the Cold War, which led to the War On Terror).
Badass Army: The Prussian (aka the North German) Army.
- The South German armies were in on it, too. One of the first heroes to make headlines through a daring reconnaissance raid was the Württemberg cavalry officer Count Zeppelin (yes, that Count Zeppelin).
Book Ends: The German Empire was unified and proclaimed in Versailles. The Empire ended there also after World War I.
Cool Train : The chief German weapon was their trains. It enabled them to get tons of troops to the front in time. As a bonus it enabled them to use reserves as front-line units without worrying about them falling over with weariness after all the marching.
Curb Stomp Battle
Crippling Overspecialisation: The expensive French Navy was built to face a peer/near-peer navy in an extended conflict that conscripts could be mobilized for. This made it useless for a quick war against an enemy with a virtually (but not totally) non-existent navy since it wasn't equipped for landing, shore bombardment or port blockading.
Eat the Dog: By the end of the war, Paris was largely free of pets, strays, and even rats since they had all been eaten during the starvation of the siege.
- Exotic Entree: Even the zoo animals were butchered for consumption by the rich. Accounts claim elephant meat is actually rather nasty, but that hardly helped class warfare sentiment that the exotic "feast" provoked in the starving masses.
The Empire: The Second French Empire is defeated, allowing for the rise of The Second German Reich.
Fielding Old Men and Boys: The French armies at later stages of the war.
Gauls With Grenades: The French had more efficient weapons, including one of the first bolt-action rifles and machine guns, though the Prussians had already used both bolt-action rifles (needle-rifles) and rifled cannons with great success against Denmark during the war that they used to get Schleswig-Holstein under their control, as well as against Austria-Hungary. It was just that the some of the other German states had not yet had equipped all their troops with such new technology.
- The rifled needle-gun was the standard Prussian infantry weapon since the 1840s (recall that in 1861 most Confederate and Union infantry units used muzzle-loaders, and a surprising number even still were equipped with smoothbores). The new French Chassepot rifle was somewhat superior (and already a second-generation weapon), but that advantage was more than offset by the breech-loading rifled artillery of the German armies, the French not issuing enough, and later French armies having to work with Civil War surplus rather than domestic French arms.
Intrepid Reporter: Otherwise famous examples include Vanity Fair founder Thomas Gibson Bowles, future famous German author Theodor Fontane, as well as past and future British MP and Truth founder Henry Labouchère.
It Got Worse: Relations between France and Germany could not be said to have improved anytime soon after this war.
- For bonus irony points: Bismarck believed that even if he were to offer France a moderate peace conditions they would eventually seek revenge for the lost war anyway. Thus, he concluded that if the second war with France is inevitable, he might as well strengthen Germany and weaken France by annexing Alsace-Lorraine. However, it was the annexation of these territories that became the main cause of the enmity between France and Germany in the subsequent decades and possibly it was the reason why the next war between Germany and France became inevitable.
Last Stand: The Siege of Paris, which lasted for roughly half the war.
- A less doomed example was Belfort, which held out till the end of the war. Being one of the few events in the war that could remotely be called a French victory (let alone one of significance), it and its leader Pierre Philippe Denfert-Rochereau were heavily lionized post war.
Magnificent Bastard: Otto von Bismarck, during the four years between the Seven Weeks War and this war he managed to isolate France while gaining an alliance with the Independent Southern German states to finish the unification process. Of course, this is the real life David Xanatos you're talking about.
- Von Moltke could qualify. Though perhaps he is more a Four-Star Badass.
Mistaken for Spies: Then journalist (later famed German author) Theodor Fontane accidentally crossed over to territory still held by the French and suffered from this. His writings on this experience remain quite valuable for historians.
Four-Star Badass: Marshal of France Achille Bazaine, although his military rank was above four stars.
- Bazaine wasn't a badass at all: he was spectacularly incompetent, and his poor performance was a major factor in France's defeat.
Rock Beats Laser: Despite the aforementioned technological advantage of the French forces, the Prussians still crushed them easily.
The Spartan Way: The Prussian General Staff which was a number of gifted men who were originally trained to act as strategists that could theoretically institutionalize Napoleonic genius. They were picked from among the best officers, rigorously schooled, trained with war games and staff rides (taking them on a field trip into the country and asking them to evaluate the tactical ramifications of the terrain.
Underestimating Badassery: Prussia was so much underestimated that even King William didn't have proper maps of France at first because he thought he was the one that was going to be invaded.
Unwitting Pawn: Napoleon III
Warrior Prince: Both William I of Prussia and Napoleon III of France had aspirations toward this. However, that kind of thing was somewhat outdated and they looked rather out of place in the role. Although William perhaps deserves more credit then he is given. He had two Magnificent Bastards, (von Moltke and Bismarck) working for him and managed to keep them working as a team to optimal level.
- The Prussian Crown Prince Frederick (later Emperor Frederick III) commanded the 3rd German Army, which contained most of the South German contingents. His cousin Prince Frederick Charles commanded the 2nd Army, while Crown Prince Albert of Saxony commanded the 4th.

Depictions in fiction

Literature

Recycled in Space by Poul Anderson in People of the Wind. A German speaking city becoming famous for its bravery on the French side inspired him to ponder the distinctions between ethnic and political loyalty and write a story of an interstellar war between aliens and humans where the humans living among the aliens take the aliens' side.