Like all great fiction, it's constantly got a bloody, probably severed toe dipped in reality
There is, obviously, a lot to Game Of Thrones that author George R R Martin has made up. Dragons, for example. Or the Undead Ice King, for another. Quite clearly fictional.
However, anyone with a passing interest in history will be able to draw some pretty defined parallels between some of the plot-threads in the previous five seasons of Game Of Thrones and some of the truly horrific stuff that has actually happened in real life.
THE LANNISTERS & THE STARKS
In Game Of Thrones, these two families absolutely hate each other, with decades and centuries of murder and violence, with some particularly noticeable similarities to the real life Lancaster and York families from 15th century England.
The two families were constantly at war, and after one particularly nasty battle, most of the Yorks were killed, and their leader, Richard II, was decapitated and had his head put on a spike (sound familiar?).
When the young boys Richard and Edward York (see: Bran and Rickon Stark) discovered their father was dead, they were looked after by his brother, Richard III (son of Richard II), until Edward was of age to take up the throne of the York family.
However, the young boys "went missing", and Richard III took the throne for himself... read into that however you wish.
Then there was the young Edward Of Lancaster (see: King Joffrey), believed it be an illegitimate son but still an heir to the throne, who was famed for stabbing some of his best friends out of boredom. Which probably explains why he didn't live too much longer passed his 18th birthday.
These violent mad-men on the show were initially led by Khal Drogo, leaving a sea of red behind anywhere they went in the show. In reality, things weren't much different, if you can join the dots to their obvious inspiration, The Mongols.
Across the 13th and 14th century, the Mongols savagely murdered, raped and pillaged their way across Europe and Asia, often only leaving a very few survivors to spread the word of their hideous natures.
Civil war eventually brought the Mongol Empire down, but not before they had conquered all of China, and some of them even went on to establish the Yuan Dynasty there... which is kinda cool.
THE WILDLINGS BEYOND THE WALL
In the show there's a massive wall that has been built in order to keep the cold and chaos at bay, but as we're constantly reminded, "Winter is coming."
In reality, back in the 2nd century, the Romans actually built an eighty-mile wall across Northern England to keep the savages (of what is now Scotland) at bay.
A couple of hundred years later, in mid-4th century, some ticked-off Romans decided to show the English just what it was they were being protected from, and allowed a couple of large groups of marauders to pretty much way waste to everything they touched.
Shooting forward a millennium or so, you can read all about the Sawney Bean Family (see: The Thenns) in 16th century Scotland, who 14 children and 32 children, mostly through incest, and were famed for startling strangers in forest, hacking them to beats and eating the remains.
THE WAR OF THE FIVE KINGS
If you're looking for a shorthand synopsis for what exactly Game of Thrones is all about, it's this: King Robert Baratheon died, and now the Baratheons, the Starks, and the Greyjoys are all killing each other to replace him.
Looking to Europe, the 100-Years' War, which took place over 116 years (don't ask) during the 14th and 15th century, can also be shorthanded: everybody wanted to be King Of France. It resulted in hundreds of thousands of deaths, with the most famous being the 19-year-old Joan Of Arc, who was burned at the stake for herecy.
Which, when compared to the way some folk have been killed in Game of Thrones, is probably considered by the show's writers as getting away lightly...
THE RED WEDDING
Still one of the most talked about episodes of television - not just of Game of Thrones, but of the entire history of television - seen some happy families at a wedding reception getting killed in some shocking, brutal ways. After the death of Rob Stark, we had only just begun to settle into a sense of comfortability with the show, and then it snaps the rug out from under us, murdering a handful of fan favourites in just one scene.
The Black Dinner, which took place in 1440 Scotland (what is it with Scotland??), is pretty much the most messed up play-date you've ever heard of.
King James II was only ten years old when his minders invited 16-year-old William Douglas, who was the leader of a powerful Scottish clan, as well as William's little brother David along for a weekend of fun in James' castle.
The three lads were getting along famously, when James spotted that his minders had put a black bull's head on the feasting table, which was pretty much the 15th century equivalent of "Take cover, cos things are about to go down."
James pleaded with his elders not to kill his new besties, but they didn't listen, and William and David ended up in the same state as the black bull.