The first official reference to a Militia in Alderney was in 1657 when Captain Nicholas Ling was transferred to Alderney from Sark as Governor and Commander of the Militia. It is quite possible that some form of Militia had existed in Alderney for centuries especially with the Islands close proximity to France.

During the English Civil War both Guernsey and Alderney supported the Parliamentarians and in 1642 an Officer from Guernsey was ordered to ensure that the defences in Alderney were in place to protect the Island from the Royalist forces in Jersey.

In 1781 new uniforms were issued to the Alderney Militia when Thomas Le Mesurier became the Governor. From this time the command of the Militia was in the hands of the Le Mesurier family for the next 100 years. The Alderney Militia consisted of 200 men and like the Militia of the other Channel Islands, the uniforms, arms and equipment were provided by the British Government. Service was compulsory, every man between 16 and 60 was mobilised "to carry Arms and do duty whenever the Governor deems it necessary to require his services".

In the early 19th century the Alderney Militia consisted of an Infantry Company, an Artillery Company and a small troop of Cavalry made up of 12 Troopers, a Cornet (2nd Lieutenant) and a Sergeant, which complemented the Infantry and Artillery. This Cavalry unit was only short lived and was disbanded prior to 1830.

The Alderney Militia became 'Royal' in 1831 along with Jersey, Guernsey and Sark, on the occasion of the 50th anniversary of the Battle of Jersey. Regimental Colours had been presented in 1825, these were laid up in the Parish Church of St Anne where they remain to this day.

The Infantry Company became gunners in 1855 when they joined the Artillery, which according to a War Office Report in 1869 numbered 275 Officers and Men. The annual cost to the British Government was £360 with a further £22 borne by the States of Alderney. The Royal Alderney Militia provided a vital contribution towards the Islands defences, and the fixed armaments at Fort Albert and Roselle Point were manned solely by Militia Gunners.

In 1928 compulsory service was ended and the Militia was reorganised as a volunteer service. The Royal Alderney Artillery and Engineers Militia sent a considerable number of men to the 9th Divisional Ammunition Column, which was raised in Guernsey in 1916 during the First World War for service with the British Army and formed 112 Company (later Battery RGA) which served in France.

Following a review of the strategic value of the Channel Islands by the Committee of Imperial Defence in 1925, a recommendation was put forward that all regular troops were withdrawn from the Island, and also that the British Government would no longer bear any cost in connection with the Channel Islands Militia forces. The Royal Alderney Militia was subsequently placed in a state of 'suspended animation' in 1929. and the guns were removed from Fort Albert and Roselle Battery. In the 1930's the War Department sold the Victorian Forts and Batteries by Public Auction and handed other large defences over to the States of Alderney. The Militia was briefly re-formed in 1935 when it paraded for the Jubilee of King George V.

On 1st September 1984 Colonel P.F.Walter MBE MC, a former Officer with the SAS, raised an Army Cadet Force which took the title of the Royal Alderney Militia (ACF). This unit is still operating and ensures that the name of the Alderney Militia lives on.