The increase in the efficiency and efficacy of guns as artillery weapons is reflected in the changing styles of military architecture.

On the defensive front, walls became thicker, often having the thickness increased further by earthen revetments to absorb shot. Walls also became lower, to provide a less easy target and to improve stability.

On the offensive side, the requirements for mounting large pieces of ordinance and supplying them with powder and shot led to the introduction of the casemate and powder magazine.

The coastal forts built by Henry VIII around the south coast of England show the first major stage in this process, with their low semi-circular bastions designed purely for the mounting of artillery pieces.

The presence of slits for archers or musketeers demonstrates that hand-held weapons would still play a part in the event of close-quarter combat, if this were necessary.

During the 17th and 18th centuries new ideas, from Holland in particular, brought about the next major revolution in design, with the introduction of the "Star" fort.

The principal features of this design were the triangular bastion, and the careful calculations required to ensure that the artillery weapons had the most efficient field of fire. Contemporary plans demonstrate this process quite clearly.

Older castles were often redeveloped to accommodate the new strategy, Carisbrooke Castle on the Isle of Wight being one example.

While the Civil War period produced mainly hastily-dug, temporary earthen structures, later periods saw the introduction of brick or stone revetments, and an increasing complexity of plan.

Not only were existing fortifications improved, as at Dover in Kent or Tilbury in Essex, but new sites were built from scratch with the new design principles. A really good example here is Fort George in the Highlands of Scotland.

Such was the efficiency of these new forts, that their features were still being used in the 19th and early 20th centuries for the "Palmerston Forts".

The major innovations were now in the design of the artillery weapons themselves, particularly the introduction of rifling and the breech-loading gun, along with improvements to the explosives used for both propellant and charge.

It should be mentioned that the idea of the breech-loader was not actually that new, there being existing examples from the 15th century!