At the outbreak of the War, there was a surplus of some 20-30,000 men on the Reserves of the Royal Navy who would not find jobs on any ship of war. It was recognised that this was sufficient to form two Naval Brigades, and a Brigade of Marines.

The Royal Marine Brigade was formed at once, and was moved to Ostende on 27th August 1914, although it returned 4 days later. On 20th September it arrived at Dunkirk with orders to assist in the defence of Antwerp. The two other Brigades moved to Dunkirk for the same purpose on 5th October 1914. In the haste to organise and move the units to Belgium, 80% went to war without even basic equipment such as packs, mess tins or water bottles. No khaki uniform was issued. The two Naval Brigades were armed with ancient charger-loading rifles, only 3 days before embarking.

The Division was originally titled the Royal Naval Division, and was formed in England in September 1914. At this stage, it had no Artillery, Field Ambulances etc.