Wounded servicemen are set to compete for the first set of medals in track and field events at the inaugural Invictus Games in London.
Prince Harry praised competitors, many still serving soldiers, from around the globe for their stories that "move, inspire and humble" as he launched the event on Wednesday night.
The sporting spectacular began with a rousing military-themed ceremony that celebrated the achievements of injured, wounded and sick servicemen and women, ahead of action getting under way later on Thursday.
Inspired by the US Warrior Games, Prince Harry vowed to bring a larger event to the UK and now teams from 13 nations, including the US, will compete over four days in a range of challenging sports.
The competition will begin at Lee Valley Athletics Centre with athletics, culminating in the 4x100m relay, before other sports such as wheelchair basketball, wheelchair rugby and swimming follow later in the week.
In the Queen Elizabeth Olympic Park, the home of London 2012, Harry was introduced by US first lady Michelle Obama who had recorded a video message for the launch.
The prince told the 6,500 spectators who had watched the opening ceremony: "No longer are these inspirational men and women defined by their injury but as athletes, competitors and team mates.
"Over the next four days we will see some truly remarkable achievements. For some of those taking part, this will be a stepping stone to elite sport but for others it will mark the end of a chapter in their recovery, and the beginning of a new one."
He ended with the passionate words; "Finally, I would like to thank you for the tremendous example you set. Your stories move, inspire and humble us. You prove that anything is possible, if you have the will."
Mrs Obama, who welcomed Harry to the White House last year, said in her message: "So to all of the competitors here today I just want you to know how incredible you are. You're inspiring all of us, especially our young people.
"Inspiring them to believe that if we dig deeper, if we work harder and confront the adversity in our own lives with just a fraction of the courage you show every day, there is nothing we can't achieve."
Competitors from Afghanistan led the parade of teams and they received a standing ovation from the 6,500 spectators who filled stands in the shadow of the Olympic arena.
The crowds remained on their feet as the Afghans were followed by athletes from across the globe.
Unsurprisingly the largest cheer was for the UK team of 131 military men and women who, like their competitors, feature those still serving and veterans.
Many of those who entered the arena had prosthetic limbs or used wheelchairs.
Among the audience was the Prince of Wales, Duchess of Cornwall, Duke of Cambridge and David Cameron, who had returned from Scotland where he had been on the Scottish referendum campaign trail with other party leaders.
Missing was the pregnant Duchess of Cambridge, who is still suffering from acute morning sickness, and will also be absent from Thursday's opening athletics events.
The opening ceremony had begun with the deafening roar of a Red Arrows fly-past, and they trailed red, white and blue smoke over the Olympic Park.
Golden Globe award-winning actor Idris Elba entered the arena in a Heritage Land Rover, used in the past by the Queen and the late Queen Mother during the 1970s and 1980s.
The Luther star read the Invictus Poem - from which the games' slogan I AM is taken - by William Ernest Henley.
A few moments later soprano Laura Wright strode onto a platform in the middle of the arena and performed Invincible, a piece written and recorded specifically for the games.
Invictus Games chairman Sir Keith Mills told those watching the ceremony, elements of which were broadcast live on BBC1:
"This evening we welcome the competitors and the friends and families that have supported them from 13 countries.
"Over the next few days we will experience some fantastic sport from some of the extraordinary competitors you see this evening. I am sure you will all join me in wishing them the very best of luck."