During David Benioff and DB Weiss’s original pitch to the premium cable network, they promised their adaptation of George Martin's A Song of Ice and Fire series would become the channel's biggest show.
However, HBO took some convincing considering it had squandered $100m on Rome, which it cancelled after just one season a few years before.
The one thing steering then HBO president Michael Lombardo to giving Thrones the go-ahead was the fact he believed it would not feature a lot of battle sequences, something Benioff and Weiss falsely reassured him on.
In new book Fire Cannot Kill a Dragon, Benioff and Weiss revealed "the show was exactly what we told them it wasn't".
"The lie we told was that the show was 'contained' and it was about the characters" Benioff said.
The duo took a gamble that nobody at HBO had read the best-selling novels.
"We knew most of the people making the decisions were not going to read four thousand pages [of Martin's books] and get to the dragons getting bigger and the [major battles]," Weiss said.
"We were banking on them not finding out until it was too late."
Game of Thrones began in 2011 and drew to a close with a divisive finale in 2019.