While Prince Philip held a number of honorary military titles during his lifetime, he also had a distinguished active service career.
The Duke of Edinburgh joined the Royal Navy in 1939, though admitted his uncle, Lord Mountbatten, played a part in that choice, with Philip also considering joining the Royal Air Force.
"I think, left to my own devices I think I probably would've signed up for the Navy," he said in a 1995 interview with Richard Astbury.
"I was eventually persuaded by my uncle, Lord Mountbatten, that it might be more sensible to go into the Navy."
"If I joined the Air Force, I wouldn't be here now," the Duke added, suggesting he may not have survived the war had he joined the RAF.
When he took his entrance exam for the Navy, Philip passed 16th out of 34 successful candidates.
However, in the interview portion of his entrance assessment, Philip stood out, scoring 380 out of 400 marks.
Graduating as the best cadet in his class from Dartmouth's Royal Naval College, Philip was appointed a midshipman in January 1940.
The young officer spent two months on the battleship HMS Ramillies, before being transferred for brief spells on HMS Kent and HMS Shropshire.
Watch: Prince Philip talks about why he chose to join the Royal Navy.
"We lived in fairy spartan conditions," said the Duke of Edinburgh recalling his time on Ramillies, in the 1995 interview.
"There was no air conditioning and we had a bathroom and just a space where we kept sea chests with our kit in it.
"It was so hot down there, we didn't sleep down there, we had campbeds on the upper deck."
Asked if he was treated as "one of the boys" during his early years of service, Prince Philip said the Royal Navy was used to "curious people" such as himself.
"The captain of Ramillies was a fellow called Bailey Growman, and he made me what was called his 'doggy', which was a sort of midshipman assistant.
"He did it because he'd been my grandfather's doggy."
Lord Lewin, a First Sea Lord and Chief of the Defence Staff, questioned years later why Philip was moved "so early" from Ramillies.
"Were they trying to keep him away from the war?" he is quoted as saying by Duke of Edinburgh biographer Tim Heald.
Asked whether it bothered him being kept away from "heavy action", the Duke recalled: "It didn't bother me [as a prince from a neutral country] very much because the ships I was sailing in were out there anyway.
"I was moved out of Ramillies when she went to the Mediterranean, I was moved out of [HMS] Kent when she went to the Mediterranean and then I went to [HMS] Shropshire.
"When the Italians invaded Greece, they lifted the ban [on him serving] and I was sent to join [HMS] Valiant in Alexandria."
Following Italy's invasion of Greece in October 1940, Philip was transferred to HMS Valiant, a battleship equipped with radar and anti-aircraft guns, in the Mediterranean in January 1941.
It was here where he was involved in the Battle of Crete, and mentioned in dispatches for his role in the Battle of Cape Matapan.
Lord Lewin served for a time with Philip on Valiant, and remembered in Tim Heald's 'A Portrait of Prince Philip' that the royal was "unusual" as he was transferred to the ship on his own.
After wrongly assuming Philip would be "favoured" due to his royal status, Lord Lewin remembered: "He could more than hold his own, gave as good as he got, and had no airs and graces."
Philip remembered Valiant had been through a "major refit" just before the Second World War, having been used during World War One, with turrets acting as anti-aircraft towers.
"Within two or three days of joining, we went out and there was a great bombardment of the Italian-held port of Bardia, in north Africa," he recalled.
"A lot of 15-inch guns going off, which I hadn't heard before and it made even big ships like that rock about a bit.
"Then the Italians had the effrontery to shoot back – it was quite interesting to hear these things whistling over and landing in the water with a great splash beside you.
"You suddenly realised that life was for real.
"Very soon after that, we were taking a convoy to Malta and there was a tremendous attack on the whole fleet by German dive bombers," he added.
"There was so much going on... it wasn't a question of fright, it was just amazement that anything like this could actually happen."
The Duke of Edinburgh recalled one experience on Valiant when "the whole ship bent" after a series of bombs hit the vessel.
During the Battle of Cape Matapan in March 1941, Valiant was among the battleships being led by Admiral Sir Andrew Cunningham, Commander of the British Mediterranean Fleet, towards a group of Italian cruisers and destroyers after receiving intelligence that British convoys would be attacked.
Philip's role was to operate a searchlight to find enemy targets while in considerable darkness.
"One of the Italian [vessels] was damaged and stopped and two other cruisers came back to her assistance during the night.
"Unfortunately for them they were detected, so... we ploughed on to where we thought these cruisers were going to be.
"Valiant actually had a rather rudimentary radar and picked up these echos which were stationary, so we assumed that's who they were.
"I got an indication what direction to point the search lights and they said 'Well, illuminate', so I switched the things by, I suppose, sheer good chance I found a cruiser.
"It picked up, we were so close, can't have been more than 2,000 yards, the beam wasn't big enough to cover the whole cruiser.
"Somebody said 'Train right' or something, because there was another cruiser and with that, everybody started shooting.
"They didn't really need much illumination after that."
The Duke was mentioned in dispatches for his efforts.
In mid-1941, following the Battles of Cape Matapan and Crete, Prince Philip headed to Portsmouth to take a sub-lieutenant exam.
The five-part test consisted of sections in gunnery, torpedoes, navigation, signals and seamanship, with marks ranging from one to three (highest to lowest) in each.
Philip scored highly achieving a 'four-one', with just one of his subjects being graded as a two.
He was subsequently promoted to Sub-Lieutenant and posted to HMS Wallace off the east coast of the UK, before becoming a Lieutenant and then a few months later, one of the youngest First Lieutenants in the Navy in 1942, taking the post at the age of just 21 while still on board Wallace.
As First Lieutenant, Philip was acting as second-in-command of his ship.
Recalling his time upon first joining Wallace, the Duke of Edinburgh said "the North Sea was a very active place".
"At night there were usually alarms about E-boat attacks, so we had to rush around and fire star shells.
"I don't think we really had a serious encounter with E-boats."
The following July, he saved HMS Wallace during an attack by German night bombers in Sicily.
With Philip's vessel having sustained some damage and being set ablaze in places, he launched a makeshift wooden raft set on fire to distract the enemy bombers, allowing his ship Wallace to escape.
The Germans returned and attacked the flaming raft, believing their initial attack had been successful, with Philip's quick-thinking having possibly saved hundreds of lives.
In 1944, Philip was posted to HMS Whelp, then a brand-new destroyer, which was headed for the Pacific and action against the Japanese.
While the ship was being constructed, the Duke lived in a hotel in Newcastle and was part of the administrative process before Whelp was commissioned.
"If you're in the services, you meet people from all walks of life," he said in the 1995 interview, when asked if this time gave him an insight into the "man in the street".
"You just live with them – the only difference is people have different responsibilities," Philip continued.
"You get to know people of every kind of background."
He was on Whelp when the Japanese surrender was signed in September 1945, escorting the USS Missouri into Tokyo Bay.
The Japanese surrender was signed on the American ship, which Prince Philip saw take place with his own eyes.
"You could see what was going on with a pair of binoculars," he said in 1995, describing the end of the war as "a great relief".
"Then they beat retreat, which you could hear going on," he continued.
"From there we went on to Hong Kong and the most extraordinary sensation when we sailed, we suddenly realised that we didn't have to darken ship anymore.
"We actually stopped in the South China Sea and 'piped hands to bathe'."
Prince Philip later remarked that Whelp was perhaps his favourite ship he served on during the war years.
After the Second World War ended, Philip was posted to Pwllheli in north Wales, and HMS Royal Arthur in Wiltshire, becoming an instructor at the latter.
Lord Charteris, who also served in the Second World War, praised Philip's contribution during the conflict, saying: "He was a very gallant officer."
Philip himself was more modest, stating in 1948, upon receiving the Freedom of the City of London, that: "We did what we were told to do, to the very best of our ability, and kept on doing it."
From early 1947, until his marriage to the then-Princess Elizabeth in November that same year, he was known as Lieutenant Philip Mountbatten, having abandoned his Greek and Danish royal titles.
He had taken the surname Mountbatten from his mother's family, and became a British subject.
King George VI made him Duke of Edinburgh on the morning of his wedding to Elizabeth.
On 20 November that same year, the couple married at Westminster Abbey – although in post-war Britain Philip's German relations were kept away from the wedding.
Following his marriage in 1947, the now-Duke of Edinburgh returned to the Royal Navy, moving with his wife to Malta in 1949, the year after Prince Charles' birth, when he was appointed First Lieutenant of HMS Chequers.
The vessel was the leader of the First Destroyer Flotilla.
In July 1950, Philip was promoted to Lieutenant Commander and given his first command, HMS Magpie, that September.
According to Tim Heald, his time in charge of the frigate was a "mixture of naval routine and ceremonial visits".
Philip ended his active naval career in July 1951 with the King's health declining.
Queen Elizabeth II took the throne the following February, with the Duke of Edinburgh being promoted to the rank of commander in the Royal Navy in June 1952.
Then in 1953, he was given honorary five-star appointments in all three services, being made an Admiral of the Fleet, British Army Field Marshal and Royal Air Force Marshal.
In 2011, he was made Lord High Admiral, the office of titular head of the Navy, succeeding the Queen in the role.
Writing to biographer Tim Heald in 1990, the Duke of Edinburgh admitted: "There has never been an 'if only', except perhaps that I regret not having been able to continue a career in the Navy."
Lord Lewin, who went on to be First Sea Lord and Chief of the Defence Staff, went one step further in the 'if only' hypothesising.
He once said that had Prince Philip continued his active service in the Navy, it would have been Philip who became First Sea Lord, and not himself.
Meanwhile, Admiral Sir Mark Stanhope, who was First Sea Lord from 2009 to 2013, said: "I think there’s little doubt if he remained in the Navy he would’ve been a very, very strong contender to rise to the top and be future First Sea Lord."
The Duke, when discussing the suggestion, said: "I never imagined that I would reach such dizzying heights as my uncle [Lord Mountbatten] or Lewin."