Prince William - who will one day be head of the armed forces - began his military career more than seven years ago when he followed his younger brother Prince Harry into Sandhurst.
At the age of 23, he commenced 44 weeks of gruelling training at the royal military academy in Camberley, Surrey, where the course is designed to push new recruits to the brink of exhaustion and shape cadets into Army officers.
By signing up, he was continuing a historic family tradition of military service and he became the most senior royal in recent memory to attend the college.
In December 2006, he graduated and was commissioned into the British Army as an officer. The Queen, the Prince of Wales, the Duchess of Cornwall and William's then girlfriend Kate Middleton gathered to watch him in the passing-out parade which marked the end of his training.
William went on to join Harry's regiment, the Household Cavalry's Blues and Royals, and was promoted to lieutenant in 2007.
Continuing his career in the forces, he received his RAF wings from his father at RAF Cranwell in April 2008 after completing an intensive 12-week flying course - a feat which saw him become the fourth successive generation of the monarchy to become an RAF pilot.
He faced criticism later that month after he was allowed to practice landing a Chinook helicopter in a field behind the Middleton family home and when he flew himself and his brother by Chinook to a stag do on the Isle of Wight. The Ministry of Defence defended the flights as part of William's training.
Shortly after, he made a brief flying visit to RAF detachments at Kandahar Air Base in Afghanistan to meet frontline troops.
But while Harry has completed two deployments to Afghanistan, William, who has always insisted he wants to be able to fight in war zones despite being a future king, has yet to achieve his ambition.
Harry revealed earlier this year that William was envious of his tours.
"I think there is a bit of jealousy, not just the fact that I get to fly this, but obviously he'd love to be out here. And to be honest with you, I don't see why he couldn't," Harry said.
In June 2008, William began a two-month attachment with the Royal Navy to help familiarise him with all aspects of the armed forces.
He joined a Royal Navy rescue team on a hurricane disaster exercise in the Caribbean and, while on board frigate HMS Iron Duke, took part in a drugs bust that seized more than one tonne of cocaine from a speedboat in the North Atlantic.
In September 2008 it was announced that William wanted to become a full time RAF search and rescue pilot.
"The time I spent with the RAF earlier this year made me realise how much I love flying," he revealed.
He began training in January 2009, later completing advanced helicopter flying training at the Defence Helicopter Flying School based at RAF Shawbury near Shrewsbury in Shropshire and undergoing the search and rescue conversion course at RAF Valley in Anglesey, North Wales
"Flight Lieutenant Wales" became a full-time operational search and rescue pilot at RAF Valley - albeit with time off for royal appearances - and has been serving with C Flight, 22 Squadron, on Anglesey since September 2010.
A typical tour for a pilot in the RAF Search and Rescue Force (SARF) is 30 to 36 months.
William carried out emergency missions in a Sea King helicopter to rescue stranded climbers and stricken vessels. His first rescue as a fully operational pilot was in October 2010, helping a man who fell seriously ill while working on a gas rig in Morecambe Bay.
The Duke, who qualified as an operational captain in 2012, giving him overall control of his helicopter, has spoken of his ''calling'' to save lives.
In an interview for BBC Wales documentary Helicopter Rescue, he said: ''There's no greater feeling than when you've actually done some good and saved someone's life.
''I don't think there's any greater calling in life... to be able to see a son or daughter's face when you bring their mother or father back from the edge of death - it's quite powerful."
He has also described his close bond with fellow crewmates, describing them as a family.
During February and March last year, the Duke spent more than six weeks flying search and rescue missions in the Falkland Islands, but his deployment caused a diplomatic row with Argentina.
William, who will one day as king be head of the armed forces, holds several honorary military appointments. He was made Royal Colonel of the Irish Guards in 2011 and wore the regiment's red tunic at his wedding.
He is also Commodore-in-Chief of Scotland and Commodore-in-Chief of Submarines and Honorary Air Commandant of RAF Coningsby near Lincoln.