The Invictus Games for wounded servicemen and women have opened at the Queen Elizabeth Olympic Park in London.
The Games, organised by Prince Harry, will see competitors from 13 countries take part in events over four days.
The Prince of Wales, the Duchess of Cornwall and the Duke of Cambridge attended the opening ceremony, along with 6,500 spectators.
Prince Harry, who was introduced by US First Lady Michelle Obama, said "lives will be changed" by the Games.
He told the crowd: "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.
"Either way, you can be sure that everyone who takes part on the track, pool or field of play will be giving it their all. And I have no doubt that lives will be changed this weekend."
In a recorded message, Mrs Obama told competitors: "Some of the most inspiring moments I have had as First Lady have been when I have met with wounded warriors like so many of you.
"You tell me how you are not just going to recover, but you are going to thrive."
She added: "While I can't hide that I hope Team USA brings home a few golds, I want you all to know how proud my husband and I are of you and how humbled we are by your example".
The event began with a shortened version of God Save the Queen, followed by the Invictus fanfare and a flypast by the Red Arrows.
The actor Idris Elba read the poem Invictus by William Ernest Henley, before the teams emerged to cheers from the crowd.
There were also ceremonial displays by military units including the King's Troop Royal Horse Artillery.
The 13 nations appeared in alphabetical order, led by athletes from Afghanistan and culminating in the appearance of the host team from the UK.
The countries taking part are: Afghanistan, Australia, Canada, Denmark, Estonia, France, Italy, Georgia, Germany, the Netherlands, New Zealand and the US.
More than 400 competitors, both serving military personnel and veterans, will go head to head in nine adaptive sports at the Olympic Park and Lee Valley Athletics Centre in London from Thursday.
After Prince Harry's speech, three singers from the Armed Forces performed the Invictus Anthem, written by Coldplay frontman Chris Martin.
They were joined by the Urban Voices Collective, the Countess of Wessex's String Orchestra and the three service bands.
Invictus Games in numbers
- More than 400 competitors
- A 130-strong British team
- 13 countries represented
- Four days of competition
- Competitions in nine adaptive sports: Athletics, swimming, powerlifting, indoor rowing, sitting volleyball, road cycling, wheelchair basketball, wheelchair rugby and archery
- Five venues, including those used during the 2012 London Olympic Games
- ..... and all only six months since Prince Harry launched the games.
See here for more coverage of the games
Invictus Games chairman Sir Keith Mills told the ceremony: "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."
He added: "When Prince Harry conceived the Invictus Games he hoped they would be an inspiration for all of those that have been wounded, injured and sick while serving their countries.
"I have no doubt that these games will achieve that and much more."
On Tuesday at a "curtain raiser" event, Prince Harry said he had had some "sleepless nights" in the run-up to the Games, which are his brainchild and based on the Warrior Games in the US.
"The Americans made it, I stole it, and we made it bigger," he said.