This is the latest in a series of occasional articles on the shared histories of Bermuda and the United States, which celebrates the 250th anniversary of its independence this year. The articles, by Heritage Matters author Edward Harris, will run throughout the year.

As we embark on the last sector of the voyage to illustrate the refortification of Bermuda in the Rifled Muzzle Loader (RML) period, 1860s to 1890s, a little review of the subject and the works caused by the increasing strength and potential unfriendliness of the United States is in order.

Sort of like a new chart for unmapped waters, full of political shoals and diplomatic reefs between our sovereign and his former adolescents …

Bermuda, through its fortifications heritage, is a fine case study for the military evolutions of the 1800s, perhaps one of the greatest centuries of change ushered in by the Industrial Revolution in Britain, one of the smallest but ultimately most influential countries of Europe, indeed worldwide.

Sadly, its diminished military, once a world-force, seems unwilling, if not incapable, of stemming present attacks on Old Blighty. On top of that, they appear to be in the rear of the current military revolution of drone warfare, some would say brilliantly developed at warp-speed by Ukraine.

As we mentioned earlier, it may have been at Bermuda that the old castle-style “bastioned trace” of fortifications (of which our Dockyard may be a final example) gave way to the “polygonal trace” exhibited in the 1820s by Fort Cunningham.

Some attribute the transition to the French, an ancient (and perhaps present) enemy, and the German army, but we stake a claim to be very early in the new game, also including Forts Victoria, Albert, George and William.

At the same time, the centuries-old domination of cast-iron, muzzleloading cannon, with round balls, was coming to an end. Indeed, new British developments in armaments in the 1850s could be said to be literally spelling the death of the cannon and its partner, the defendable fortification. The round balls of the Her Majesty Vicky’s Army became elongated projectiles, loaded from the rear, as new guns and propellants were developed from that time onwards.

As conversions of guns and forts took place in the east, out west the Dockyard — the bastion of the Royal Navy at the “Gibraltar of the West” (Bermuda) — saw its 120-odd cannon melted into the scrapyard of history, to be replaced with 21 RMLs.

A fine example of that type of new gun is to be found at the “Steinhoff Bastion” at the National Museum, now a part of and a protector of the Dockyard Heritage. Of course, as “gun steel” had not yet been invented, the RMLs were made of wrought and cast iron and still loaded from the muzzle.

Five18-ton RMLs were mounted upon the old bastions of the “Keep”, the ten-acre fort of last resort of the Dockyard fortifications with its great and internationally important Commissioner’s House, now the nerve centre of the National Museum.

Fifteen smaller 64-pounder RMLs were emplaced in between the larger guns of the Keep and on the ramparts of the Land Front of the Dockyard, while the last of the big guns was put on “Bastion H”, on the Northwest Rampart, fronting the sea.

Coincidentally, the stone dockyard, replacing the original buildings of timber, was only completed in the late 1860s, just in time for some of its features to be remade to take the new period of guns.

The purpose of all the new, revised and rearmed forts in Bermuda in the 1860s to 1870s was to protect the Dockyard, which, with bases in the Canadian Maritimes and the British West Indies, represented the imaginary western Atlantic border of Great Britain.

As the lynchpin of that military line, Bermuda maintained its importance to the United Kingdom into the 20th century, when friendship would break out with the United States of America, an eruption of worldwide import. An earlier capture of Bermuda and its Royal Naval Dockyard would have been a great prize for the United States!

• Dr Edward Harris is the founding executive director emeritus of the National Museum of Bermuda