U.S. television network HBO has released a trailer for the second season of the popular series "Game of Thrones". The serial is based on a popular fantasy book series, "A Song of Ice and Fire" written by American George R.R. Martin.

The second season's trailer, called "Shadow" runs for one minute and seven seconds. The season itself is reportedly based on Martin's second novel "A Clash of Kings".

The first book in Martin's series - "Game of Thrones" - was the first of a planned series of seven novels. HBO adapted the first novel as a television series and the show debuted in April, 2011.

Set in the Seven Kingdoms of Westeros, "Game of Thrones" depicted the struggles and fates of the dynasties ruling the seven kingdoms - the North, the Vale, the Stormlands, the Reach, the Westerlands, the Iron lslands/Riverlands and the Dorne - as they battle for the Iron Throne.

The first season opened to considerable critical acclaim and won several awards, including one for Outstanding Performance by a Stunt Ensemble in a Television Series, at the 18th annual Screen Actors Guild Awards, which were held on Sunday in Los Angeles, California.

The second season of the "Game of Thrones" will be a ten-episode series, to be aired on HBO from April 1, 2012.