Have you ever looked closely at the peak of a Western general's uniform cap — or that of an admiral or chief of police — or at their epaulettes?

If so, you'll have seen that they are commonly decorated with embroidered gold thread depicting oak leaves and acorns.

The type of oak they display (Quercus robur; English oak) is common in Britain and most parts of Europe. This species of tree is close to the Japanese nara (Quercus serrata) or mizu nara (Quercus mongolica).

Oak leaves and acorns were probably first used as a symbol of martial power by the ancient Romans, to whom the felling of oak trees was symbolic of conquering the forest-loving Celts who once held sway over much of central and western Europe, Iberia, northern Britain, Wales and Ireland.

To the Celts past and present, the oak was and is a sacred tree, and in times past anybody cutting one without special permission and elaborate ceremony would in turn have their head cut off at the stump of the felled tree.

The Celts of yore did not have churches or temples, they worshipped in sacred oak groves. The word for oak in Celtic is dur or dru. This gave the name to the Celtic shamans, the druids — meaning, "men of the oak" — and also found its way into modern English in words such as durable, duress, duration, endure and so on.

In essence, the English oak, with its 400- to 500-year lifespan, was a symbol of long-lasting toughness and strength.

Later, in Britain, permission to cut oaks could only be granted by the king, a concession that showed he had given to his general, admiral or lord, the right to build a castle. Stone castles need stout oaken beams at the heart of their construction, and few timbers other than teak and ironwood can rival oak's strength .

Once, when my Dad, a Royal Navy man through and through, returned home from a long voyage aboard the battle-cruiser HMS Birmingham, my mother and I went to meet his ship when it returned to its home port of Portsmouth in the South of England. What a grand day that was, with bands playing, other ships sounding their horns and many hundreds of people cheering.

That night my parents seemed to be somewhat busy, but the next day my Dad, resplendent in his uniform, gave me a special treat and took me aboard the great battleship HMS Victory, built between 1759-65, that remains a commissioned warship preserved in all its glory in dry dock at Portsmouth Royal Naval Dockyard.

With a displacement of 3,500 tons, HMS Victory was Admiral Horatio Nelson's flagship at the Battle of Trafalgar on Oct. 21, 1805. In that epic encounter, the British fleet soundly defeated Napoleon's fleet of French and Spanish ships off the coast of Spain at a time when HMS Victory was already 40 years old and a veteran of many battles and long years at sea. Victory in that battle was the major reason why Napoleon could not invade the island nation of Great Britain, as, without his fleet of warships, the Royal Navy would have sunk any invasion force he tried to ferry across the English Channel.

Though HMS Victory no longer sails, the magnificent vessel remains preserved in perfect condition with its 112 guns on three decks. In action, its crew would have numbered about 900 men, boys and officers.

Can you imagine how proud I was as a boy to be going around that great historic ship with my tall, handsome, suntanned Dad in his uniform? We had just paid homage at the place where Nelson breathed his last — for he was killed aboard HMS Victory during the Battle of Trafalgar — when my Dad said something that stuck in my mind.

"Do you know why Britain was able to build such a fine ship as this?" he asked.

I answered that it was because we had good shipbuilders and sailors.

Dad nodded. "Yes, that's true, but this one ship alone took 2,000 big oak trees and about 700 trees of other kinds — pines, elms and so on — to build. That's 2,700 big fine trees — in other words a whole wood, just for one ship."

In the days of sail, only the nations that had great forests had navies, and the best ships of all were built of oak.

Another vital factor that enabled the sailing ships of the European nations to go on long sea journeys was the barrel, a container made of oak and bound with iron. Barrels held water, wine, spirits such as rum or brandy, salt meat, salt fish and gunpowder. They were sturdy, long lasting, did not leak, and could be efficiently stored. Enormously heavy barrels could be moved along by one or two men and hoisted up by ropes, with manpower greatly enhanced by dint of pulleys, blocks and tackle.

Ever since I began researching the four navy novels I have written spanning the period of the Anglo-Japanese Alliance (1902-21), I have been on excellent terms with Japan's Maritime Self-Defence Force. Consequently, for each of the last 10 years I have been asked to give a lecture on naval history to the officers and officer cadets of the MSDF College in Etajima, Hiroshima Prefecture — formerly the most famous college of the Imperial Japanese Navy.

In 2002, to celebrate the 100th anniversary of the Anglo-Japanese Alliance, I, together with Sir Stephen Gommersal, then the British Ambassador to Japan, planted an English oak in front of the great memorial hall at Etajima. It was another proud day for me, with the band playing "Kimigayo" and "God Save the Queen" (the Japanese and British national anthems, respectively).

In addition, to celebrate the anniversary, more than 200 other oak trees were planted that year in places all over Japan which had links to Britain.

Since then, every year when I visit Etajima, I go to look and see how the oak tree we planted is doing. I was there on Nov. 10., and my manager took the accompanying photograph. The tree is doing well, and I was able to tell the cadets and officers of the history and meaning of the oak tree while holding up a couple of its leaves.

If you really think of it, all of human culture and history is one way or another linked to trees, woods and forests.