Within a few months of the outbreak of war (August 1914) a line of trenches stretched from Switzerland to the Belgian coast. The Germans and their Austro-Hungarian allies were on one side of the line, and on the other there were the French and British forces and their allies. Things had reached a stalemate.
The British were keen to find ways to break the German lines. Superior sea power seemed to be the answer. The First Lord of the Admiralty, Winston Churchill, suggested several ways to use British naval resources. One of these was an assault on the Dardanelles.
This 50-kilometre-long strait, which separates the Aegean Sea from the Sea of Marmara, was, at its narrowest point (the Narrows), less than 2 kilometres wide. The aim was to pass a force into the Sea of Marmara and threaten Constantinople, which was the capital of Germany's ally, the Ottoman Empire (modern Turkey). The city guarded the Bosphorus, which is a narrow waterway that leads into the Black Sea, so the city was open to attack from the ocean.
Churchill quickly ordered a bombardment of the forts guarding the Narrows. This operation, carried out before Great Britain formally declared war on the Ottoman Empire, reminded the Turks of the threat to the Dardanelles. They improved defences, including laying minefields.
As early as November 1914, Churchill had suggested an attack on Gallipoli. His fellow members of the War Council, which decided British strategic issues, rejected his plan as too risky. The stalemate and the actions of the Ottoman Empire led the council to rethink their position.
The Turks were advancing northwards in the Caucasus, and Russia called for assistance. Russian forces soon drove the Turks back, but the mood in the War Council swung Churchill's way. There were other potential advantages of the suggested attack. The Balkan states might attack Austria-Hungary from the south-east, and a campaign in the Eastern Mediterranean might encourage Italy to enter the war on the Allied side.
The limited nature of the proposed action helped. Churchill's suggestion of a naval attack on the forts guarding the Narrows would not need a large force. Nor would it have to reduce Britain's naval position in the North Sea, since only older battleships would be used. The War Council approved the proposal on 15 January 1915.