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  ===Conception and development===
  Showrunners D. B. Weiss and David Benioff created the series, wrote most of its episodes and directed several.
  In January 2006, David Benioff had a phone conversation with George R. R. Martin's literary agent about the books he represented and became interested in ''A Song of Ice and Fire'', as he had been a fan of fantasy fiction when young but had not read the books before.  The literary agent then sent Benioff the series' first four books. Benioff read a few hundred pages of the first novel, ''A Game of Thrones'', shared his enthusiasm with D. B. Weiss, and suggested that they adapt Martin's novels into a television series; Weiss finished the first novel in "maybe 36 hours". They pitched the series to HBO after a five-hour meeting with Martin (himself a veteran screenwriter) in a restaurant on Santa Monica Boulevard. According to Benioff, they won Martin over with their answer to his question, "Who is Jon Snow's mother?"
  Before being approached by Benioff and Weiss, Martin had had other meetings with other scriptwriters, most of whom wanted to adapt the series as a feature film. Martin, however, deemed it "unfilmable" and impossible to be done as a feature film, stating that the size of one of his novels is as long as ''The Lord of the Rings'', which had been adapted as three feature films. Similarly, Benioff also said that it would be impossible to turn the novels into a feature film as the scale of the novels is too big for a feature film, and dozens of characters would have to be discarded. Benioff added, "a fantasy movie of this scope, financed by a major studio, would almost certainly need a PG-13 rating. That means no sex, no blood, no profanity. Fuck that." Martin himself was pleased with the suggestion that they adapt it as an HBO series, saying that he "never imagined it anywhere else". "I knew it couldn't be done as a network television series. It's too adult. The level of sex and violence would never have gone through."
  The series began development in January 2007. HBO acquired the television rights to the novels, with Benioff and Weiss as its executive producers, and Martin as a co-executive producer. The intention was for each novel to yield a season's worth of episodes. Initially, Martin would write one episode per season while Benioff and Weiss would write the rest of the episodes. Jane Espenson and Bryan Cogman were later added to write one episode apiece the first season.
  The first and second drafts of the pilot script by Benioff and Weiss were submitted in August 2007 and June 2008, respectively. Although HBO liked both drafts, a pilot was not ordered until November 2008; the 2007–2008 Writers Guild of America strike may have delayed the process. The pilot episode, "Winter Is Coming", was first shot in 2009; after a poor reception in a private viewing, HBO demanded an extensive re-shoot (about 90 percent of the episode, with cast and directorial changes).
  The pilot reportedly cost HBO US$5–10million to produce, while the first season's budget was estimated at $50–60million. In the second season, the series received a 15-percent budget increase for the climactic battle in "Blackwater" (which had an $8million budget). Between 2012 and 2015, the average budget per episode increased from $6million to "at least" $8million. The sixth-season budget was over $10million per episode, for a season total of over $100million and a series record.