Prince William graduated from Sandhurst in December 2006
Prince William is to follow in his father's footsteps by learning to fly aircraft with the Royal Air Force, as part of a four-month attachment, before being seconded to the Royal Navy.
The prince's brother, Prince Harry, entered Sandhurst first - and is currently serving as an officer in the Household Cavalry's Blues and Royals.
There is a long tradition of embarking on a military career in the royal family, and the young men are not the first members of today's royal family to follow a military path.
The princes' uncle, Prince Andrew, fought in the Falklands War and his grandfather, Prince Philip, saw service during World War II.
Prince Andrew joined the Navy in 1979 and, after gaining his Royal Marines green beret but deciding against joining the Marines, went on to elementary flying training at RAF Leeming, Yorkshire.
In April 1981, after being presented with his wings by Prince Philip, he left with the aircraft carrier HMS Invincible on active service during the Falklands War.
In 1997, after receiving various commendations from the forces, Prince Andrew was appointed to join the Ministry of Defence in London as a staff officer in the Directorate of Naval Operations.
His 22-year service in the Armed Forces ended in July 2001.
Prince Andrew served in the Falklands war
William and Harry's father, the Prince of Wales, took up his first service appointment in 1969 as colonel-in-chief of the Royal Regiment of Wales.
He went on to become the colonel of the Welsh Guards in 1975, in succession to the Duke of Edinburgh, and now holds a number of service appointments.
He spent six months at the Royal Air Force College at Cranwell learning to fly jet aircraft in 1971 and obtained his RAF wings.
In the autumn of that year, the prince entered the Royal Navy.
Following service on a guided-missile destroyer and two frigates, he qualified as a helicopter pilot in 1974 at the Royal Naval Air Station at Yeovilton in Somerset.
World War II
Later, the prince joined 845 Naval Air Squadron on commando flying duties, operating from the aircraft carrier HMS Hermes.
In early 1976 he took command of the coastal minehunter HMS Bronington. The prince left the Navy the same year.
He currently holds the ceremonial ranks of admiral in the Navy, general in the Army and air chief marshal in the RAF.
William and Harry's grandfather, the Duke of Edinburgh, had a distinguished military career, serving during World War II.
He joined the Navy as a cadet in 1939.
He first saw action in January 1941 on battleship HMS Valiant.
The Prince of Wales holds positions in the Army, Navy and Air Force
In October 1942 he became first lieutenant of the HMS Wallace, on which he was serving at the time, and later joined the Allied assault on Sicily and the British Pacific Fleet.
After serving with distinction on several other vessels, Prince Philip's naval career came to an end when the death of his father-in-law, King George VI, was announced in 1952.
Prince Philip remains close to every branch of service life, and is said to have influenced the decision of his children and grandchildren to serve.
Even the Queen, William's grandmother, undertook National Service at the age of 18, joining the Auxiliary Transport Service in 1945.
But not all royal military careers have been long and distinguished.
The princes' other uncle, Prince Edward, had only a brief stint in the Armed Forces.
He joined the Royal Marines - the first member of the Royal Family to do so - as a second lieutenant in 1983.
Prince Edward completed a two-week course at Lympstone before going to Jesus College, Cambridge, to read for history on a Marines-sponsored cadetship.
He subsequently spent five weeks a year with the Marines, including a short tour in Belize.
But he failed to adapt to military life and eventually left in 1987 to work in theatre production for Andrew Lloyd-Webber's Really Useful Group.