In this video, we examine how the devastating 9/11 terrorist attacks unfolded in September 2001, as the world prepares to mark the 15th anniversary of the tragedy. Almost 3,000 people lost their lives and thousands more were injured in the attacks, which targeted the twin towers of the World Trade Center and the Pentagon - both key symbols of America's global power and influence. Get the latest headlines: http://www.telegraph.co.uk/ Subscribe: http://www.youtube.com/subscription_center?add_user=telegraphtv Like us on Facebook: http://www.facebook.com/telegraph.co.uk Follow us on Twitter: https://twitter.com/telegraph Follow us on Google+ https://plus.google.com/102891355072777008500/ Telegraph.co.uk and YouTube.com/TelegraphTV are websites of The Daily Telegraph, the UK's best-selling quality daily newspaper providing news and analysis on UK and world events, business, sport, lifestyle and culture.