Here is a list of event that I would concider a part of the Civil War. Note that I don't mean events that occur in the movie of the same name, Captain America: Civil War but the event Civil War inside the universe. So, let's begin.
Events Before Civil War
These are events that does not tie in to the Civil War directly but are huge events that helped to form the conflict.
"I am Iron-Man" (2010)
The world had just been experiencing it's first of many very public abnormal terrorist attacks. With Iron Monger fighting Iron Man leaving many civilans in danger. But it was when Stark Industries CEO Tony Stark steps forward and says the now so famous words, that the people of the world is shocked. Superheroes, has just gone public.
Duel of Monaco (2011)
For quite some time Senator Stern, with the help of Justin Hammer had been trying to prove that the Iron-Man suit is actually a weapon owned illegally by Tony Stark. But Tony promised that this kind of technology couldn't exist somewhere else and wouldn't for at least 15 to 20 years. But, in Monaco on May 24th 2011. Ivan Vanko appeared. He appeared with the very technology that Tony Stark had proved did not exist anywhere else.
Battle at Culver University (2011)
Iron-Man had saved the day, the Hammer Drones was all defeated. Then suddenly, a green giant monster attacked a University in Virginia. The Monster was filmed by two of the students and was brougth to the medias attention as the Hulk. The video showed the Hulk killing multiple soldiers and damaging major parts of the university.
The Harlem Terror (2011)
Following the Hulk story. The Hulk once again showed up, but this time in New York, and with a friend. After the battle Emil Blonsky was praised as a hero and even wanted on the Avengers by the World Security Council.
Battle of New York (2012)
After rumors of a godlike man appearing in Germany, the masses didn't really know what to think. This was until an Alian army charged down from a hole over New York. This was a battle that destroyed mayor parts of the city, mostly Hell's Kitchen. The damages where up to 18.8 Billion Dollars. This was also the first time civilas where caught in the crossfire of an enhanced terrorist attack. 74 people lost their lifes that day including civians and police officers. This became a huge event going forward, since everything happening from now is because of this.
The Terrorist Attacks of the Mandarin (2012)
The Chinese theater blowed up and a man who called himself The Mandarin showed up to take the credit. After a daring attemt by Tony Stark to threaten this new Mandarin-guy. He blew up Tony Starks house. The Mandarin turned out to be only a crazy actor. The real terrorist was a man named Aldrich Killian and his goal was to assasinate the president. Which he almost did, if it werent for Iron Man and War Machine. But this event made people scared of superpowers. Because it showed that people actually had them, and not all of them where good.
Hydra Upising (2014)
S.H.I.E.L.D. the organization in place to protect the world from alians and powered people suddenly had airships raing down over Washington DC. 23 Civilians died that day and so many more go letters sent home about their relative who they didn't even know was an secrent agent, either telling them that they had gone bad or that they died in battle. This event showed the people that no one could be trusted.
Hulk in Johannesburg (2015)
So Bruce Banner was a trusted guy, he even helped to save New York back in 2012. But May the 3rd the Hulk attacked Johannesburg. And the situation did not get better when Iron Man showed up. The two fought and destroyed the city and many civilians and members of the South African Police Service died.
Battle of Sokovia (2015)
One of the most violent batlles the people had seen in years. Ultron, a robot designed by the Avengers. Had gone rouge and started to lift city. This was a wakeup call for many. Should the Avengers really be free to do whatever they feel like or should they be put in check? 177 people died and 484 Billion Dollars worth of property was destroyed. Now the world weht devided. They demanded change, and soon they would get it.
Events Leading up to Civil War
So until the Battle of Sokovia a Civil War wasn't even something anyone thougt about. But after this, everything went in this direction. Here I will list smaller events that will lead up to the Civil War. None of them will be as big as the ones above.
Inhuman Crisis (2015-2016)
People have starting to dissapear and people with powers have started to appear. One example of this is when a man in Seattle runs out of his appartment and starts to melt things with his hands. Cars explode, buildings colapses. And then he just dissapears. Nobody knows what they are or where they come from. Until one of those powered humans attacks a hospital in Ohio. The goverment then explains that they are Aliens, and the man who attacked the hospital was an alien terrorist named Lincoln Campbell. This makes the people affraid of the Inhumans and a group of high status peolple meet up to dicuss what to do with this crisis. They decide that the best way to do it is to build a sanctuary state for Inhumans in Russia. So that Inhumans can live in peace.
The Watchdogs is an online hate group that is angry with the Avengers for destroying cities all over the world. But their new goal is to illiminate the Inhumans. Lead by Felix Blake, the Watchdogs took a step from trolling forums to attacking buildings. On March 29th 2016 the groop attacked an ATCU building while broadcasting it. Telling people that the goverment is keeping secrets about the Aliens from the public.
The Sokovia Acords (2016)
Sokovia Accords are a set of internationally ratified legal documents that provide regulation and frame-working for the military/law enforcement deployment of enhanced individuals, particularly the Avengers. The document was established by the United Nations. The Accords was created after the people damanded more control over the Avengers after the events of Sokovia, and also New York and Washington DC.
The Civil War
The Civil War is an dissagreament between Tony Stark and Steve Rogers mainly about the Sokovia Acords. Tony thinks that the Avengers should sign the contract to show the people that they are in fact the heroes that they are. Wthile Steve thinks signing the contract makes them part of a system and can make the goverment controll the Avengers for their own will.
the Civil War will begin in Captain America: Civil War