George III may never have left the south of England or fought on a battlefield, but he explored the world through a vast collection of military maps that are now being made available online, offering extraordinary insight into the art of warfare and mapping.

Highlights include two-metre-wide maps of the American War of Independence. Known as the king who lost America, George followed the steady erosion of his hold on American colonies from the comfort of his library at Buckingham House, now Buckingham Palace.

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These huge maps were probably hung on purpose-built mahogany stands, as the king took close interest in every detail, down to how many blankets were required by the British forces.

His map of the final British defeat at the Battle of Yorktown in 1781 is the only known copy to survive outside the US. An annotation by the American mapmaker marks “The Field where the British laid down their Arms”.

Now more than 3,000 of his military maps and prints are available online on a special Royal Collection Trust website, militarymaps.rct.uk, to mark the 200th anniversary of his death, making them publicly available for the first time.

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The collection features material from the 16th to 18th centuries, from highly finished presentation maps of sieges, battles and marcheso rough sketches drawn in the field, depictions of uniforms and fortification plans, providing a vivid contemporary account of important theatres of war in Britain, Europe and America.

The collection also include maps by the Scottish military engineer William Roy, who in 1766 proposed a national survey of Britain, seen as the founding of the Ordnance Survey. George III also acquired maps from other collectors, including 16th and 17th century European military prints. A rare engraving of the Siege of Malta in 1565 shows the Fort St Elmo overrun by the besieging Turkish forces, resulting in the death of 1,300 Christian knights, captains and soldiers.

Martin Clayton, head of prints and drawing at the Royal Collection Trust, said: “It is fitting, and rather moving, that on the 200th anniversary of George III’s death we are able to make the king’s collection of military maps digitally available to all, offering new insight into his topographical interests and his contribution to the cartographic sciences.”