By Steven McKenzie
Highlands and Islands reporter, BBC Scotland news website
The Highlands played a role in preparations for the D-Day landings
Built to help fight world wars, today they are rusting hulks or brickwork shells teetering on the edge of cliffs being slowly eroded away by the sea.
Wartime relics dotted across the Highlands and Islands and Northern Isles include the remains of a flying boats station and gun emplacements.
The north of Scotland provided bases, anchorage and important training grounds for soldiers and sailors.
While the wars are long over, the sites' battle with time goes on.
An army of archaeologists and historians will be needed to record the myriad of defences, look-out posts and other built infrastructure.
Potential areas of interest include the Cromarty Firth which provided one of the safest anchorages in Britain for the Royal Navy during World War I.
During World War II, the firth was used for flying boats, which patrolled Scotland's northern coastal waters looking for German U-boats.
To the north-west of Cromarty, Loch Ewe in Wester Ross was key to the Arctic convoys delivering weapons and supplies to Russia.
So many vessels massed in the loch before sailing for Murmansk, it was said a person could walk across the ships from one shore to the other without getting their feet wet.
Fairy Lochs, near Gairloch, Wester Ross, is also a war grave for the nine crew and six passengers of a US Liberator bomber which crashed on 13 June, 1945. The aircraft was returning to America when it came down.
Remains of its engines and propeller blades can still be found scattered across the area, or submerged in lochans.
Nicola Taylor, curator at Gairloch Heritage Museum, said: "There is a plaque at Fairy Lochs remembering those who died in the crash.
"For some people in the States it is still somewhere they make a pilgrimage to."
She said over time the piece of aircraft will eventually disintegrate and disappear.
Meanwhile, the Highland landscape provided perfect training grounds for commandos and saboteurs of the Special Operations Executive (SOE).
Supplies and SOE agents were reputed to have passed through Mallaig to training centres in Knoydart and along Loch Nevis.
A striking memorial at Spean Bridge commemorates commandos who under went exercises in Lochaber.
Possibly less well-known is the role of Nairn's beaches for preparing soldiers for the D-Day landings.
Today, day trippers and dog walkers stroll by a modest stone and plaque recalling the area's part in one of the most famous episodes of World War II.