In the early 1900's Invergordon became an official naval base; the Firth was thought suitable because of the channel depth and frequently had visits from the Home Fleet. During the First World War (1914-1918) Invergordon was a full-scale base for the Royal Navy, providing fuel oil, water and dockyard repairs. The town's population mushroomed when 6,000 people came to work in the dockyards. The people of Invergordon were exposed to the horrors of war when, at Hogmanay in 1915, HMS Natal blew up in mysterious circumstances with a loss of over 300 lives. Some 'Natal' gravestones can be seen at Rosskeen churchyard.
In 1931, at the time of the World depression, the British Government announced huge pay cuts. When the Atlantic Fleet returned to the Firth whilst on manoeuvres, meetings of the below-deck crew were held in Invergordon and a policy of passive resistance was agreed - no ships would sail from the Firth. Although this is known as the Invergordon Mutiny, no ships were taken over and no officers captured. Within days however the fleet was slowly leaving and sailing to its home bases in the south. The effect of the 'mutiny' had caused a run on the Government's gold reserves and in the short term the pay cuts were reviewed and reduced.
During both World Wars the harbour and oil storage tanks were of great value to the Royal Navy. Before, during and after the last War these facilities were improved but the contraction of the Admiralty after the Second World War reduced the base to a fuelling port.