...And so is love, but that's another trope.
Louis Armstrong once had a song by the title of "What a Wonderful World". Which is pretty much the opposite of what it's like when Earth Is a Battlefield.
That's because when Earth is subject to this trope, it's hard to find anywhere on the planet where there isn't violent fighting going on. Anywhere you do find that's peaceful now could easily become thick with fighting at a moments notice, if it wasn't thick with fighting previously. Nobody on Earth is untouched by loss of loved ones. And making love instead of war isn't exactly an option for anyone who's serious about coming out of this ahead. If War Is Hell, then having this trope means the underworld's unleashed its evil upon the planet, and they're having one hell of a field day.
In short, this is Exactly What It Says on the Tin. The Planet Earth has become a giant fracking battlefield, or at least a significantly widespread number of sections of it have.
Name is a pun on both the song "Love Is a Battlefield", which has nothing to do with this trope, and Battlefield Earth, which despite its name also doesn't quite fit this trope. Sometimes related to Humans Are Warriors.
- Most instances of an Alien Invasion.
- Most Gundam series fit this trope.
- In particular, the rules for the Gundam Fight of G Gundam state that "Earth is the ring"... shown by the existence of laser boxing-ring ropes circling the planet, which a Gundam actually bounces off.
- Usually everything that involved a mecha, on the principle that any discovery man kind makes, it stays in the military first (and for the rule of dramatism in the media, used for bloody wars... many many bloody wars).
- Strike Witches has Japan, Germany, Finland, Russia, France, Italy, USA and the UK fighting an Alien Invasion at the same time.
- Same goes for its spiritual predecessor Sky Girls.
- This trope is played straight in Super Dimension Fortress Macross/Robotech where all of Earth bombarded and devastated in a planet wide assault. Furthermore, this experience was the driving reason in the aborted sequel Robotech: The Sentinels for the heroes to lead a major armed expedition to the Robotech Masters' world. Ostensibly, the major goal is to come to an accord with that power, but if it comes to fighting, then at least their world will be the battlefield this time.
- The Macross continuity has humanity specifically anticipating this to happen again in the future and taking precautions.
- Cornova's Poke Wars series shows Kanto, Johto, Hoenn, Sinnoh, Orre, Fiore, Oblivia, and Almia as war torn hell holes.
- In general, it's a poplar fanfic idea, and is usually melded with Crapsack World for an apocalyptic wasteland. Any fandom with a decent amount of fiction written about it will have a variation of this.
- Earth vs. the Flying Saucers
- Battle Los Angeles
- Independence Day, even if it focused on the United States.
- Terminator: Salvation makes the trope particularly clear, with a radio message being received by sparse resistance fighters across the entire planet.
- Godzilla: Final Wars Giant monsters controlled by aliens destroying major landmarks while fighting Godzilla, anyone?
- Of course, Final Wars is essentially a remake of Destroy All Monsters which basically as the same premise. Aliens control giant monsters (Including Godzilla himself who attacks New York City) that destroy major cities.
- Battlefield Earth, albeit in the past tense (humanity was curb-stomped long before the plot gets going).
- An interesting case in Hackers, where hackers from all over the world are joining in a virtual attack on the Gibson supercomputer in order to overload its defenses.
- H.G. Wells' War of the Worlds may or may not be the ur-example in fiction, but as noted on its page, it doesn't mention what happens outside Britain.
- Adaptations generally make it clear that they landed elsewhere.
- John Ringo's Posleen War Series does this, with Posleen landings all over the place generally making life rather suck for most humans.
- The later books of the Animorphs series, after the morphing cube is stolen and Visser Three launches open war.
- World War Z - basically the complete opposite of America Saves the Day.
- The appropriately named Worldwar series by Harry Turtledove has alien landings in sites across the world in the middle of 1942. It's debatable whether Earth Is a Battlefield applies after the first three months of war: during that time the alien Race conquer and subdue most nations apart from the great powers who were mobilised to fight World War Two. However, partisan resistance continues everywhere, the area Turtledove mostly writing about being China.
- The War Against the Chtorr, and humanity is losing.
- Many episodes of Doctor Who.
- In Palladium's Teenage Mutant Ninja Turtles and Other Strangeness, this was what much of the Earth's future looked like: evacuated by all organic life and used as a killing zone by psychotic A Is hiding in underground bunkers.
- Risk, of course.
- The Command & Conquer Tiberium and Generals franchises.
- Most of the fighting in the Generals series happens in Asia. One mission in the expansion has the GLA visiting continental US to steal their newest weapon while the entire Chinese campaign happens in Eastern/Central Europe.
- And in Red Alert 2 and 3.
- Resistance Fall of Man
- Probably the Seven Hour War from the Half-Life 2 backstory.
- That was more of a Curb Stomp Battle. A more straightforward example is the uprising in the most recent games. It's humanity vs the Combine and it's unlikely the fighting is restricted to Eastern Europe only.
- The world has descended into something closely resembling this in the beginning of Metal Gear Solid 4. It's especially apparent in the fake ads that appear before the opening cutscene.
- The X-COM series is a prime example of this trope, where Earth is in the midst of a full-scale invasion of numerous alien species. So in essence, it seems that Earth has become China during the Opium war (except the aliens are pushing death and enslavement, rather than opium).
- With the debut trailer for Mass Effect 3 showing the Reapers just annihilating London and presumably other cities, it appears that the game is going to have this trope.
- The game itself starts with the Reapers invading Earth. Over the course of the game, you hear from Anderson, who is leading a global resistance movement that's fighting back against the Reapers as best as they can.
- Invoked in Strange Journey, where the first sector of the Schwartzweld, Antlia, is modeled after a burning warzone. The reason? Its Tyrant, Morax, is the embodiment of humanity's warlike nature.
- The world of Avatar: The Last Airbender.
- In the American Dad noncanon Christmas episode "Rapture's Delight", the Rapture comes and half the Earth's population ascends into heaven while the rest are left behind as Jesus returns to battle the Anti-Christ. In seven years the world becomes a wasteland in the war between the angelic forces of Jesus and the demonic armies of the Anti-Christ. One battle is mentioned, the "Battle of Boca Raton".
- The Ur Example is actually the "Seven Years' War" in the mid-18th century, which had a bunch of simultaneous conflicts sprouting up over various points in the world. The part in North America is known as the "French and Indian War". Winston Churchill himself nicknamed it "The first world war".
- World War I, though mostly confined to Europe, saw fighting scattered throughout Africa and the Middle East, and at least one major engagement in the Pacific. Nearly every state on Earth was involved either directly or indirectly.
- World War II is a more direct example, as there was a lot of fighting all around Earth, in Africa, around North America, in Europe, in East Asia and the Pacific regions. Also small naval battles around South America.
- European Christians Vs Muslims, is in a way even older then the Seven Years' War. Toward the sixteenth century onward it was a primary consideration in wars on opposite sides of the world. Catholics vs Protestants was a shorter war but in it's time had an even greater span then Christiandom vs Islamistan.