The Firth of Clyde and the long sea-lochs were centres of activity during the two World Wars. Inside the boom stretching from the West Bay to the Cloch Lighthouse on the other side of the Firth, gathered the ships bringing supplies from Canada and the USA, the great liners acting as troopships and the Royal Navy ships which protected them.

The Normandy landings of 1944 were planned and rehearsed on the shores of Loch Fyne. The daring raids on ships of the German Navy by tiny two-man submarines were the result of months of training in Loch Striven. It was also the practice area for the famous Dambusters bomb.