Once the fighting on the Western Front in France and Flanders settled into siege warfare that defied attempts by both sides to break through, some British politicians became entranced by the idea of attacking Germany ‘by the back door’. Despite pre-war Naval planning that suggested a passage of the Dardanelles Straits was impossible, the lure of an easier route to the defeat of Germany became irresistible. The pro-‘Westerners’ in the high Army command were overruled and eventually acquiesced.

The planning of the Gallipoli operations was makeshift to say the least, but it was based on land operations only being required in support of a naval breakthrough of the Dardanelles Straits.

The naval attempt to bombard the Turkish guns and forts failed, as did a half-hearted attempt to push through the Straits minefields. The Royal Navy now called on the army to capture the guns from the land side, and the door was thus opened to disaster. A Mediterranean Expeditionary Force (MEF) composed of British Empire and French troops was hastily assembled in Egypt. Among the British Empire forces were the men of the AIF (Australian Imperial Force) and the NZEF (New Zealand Expeditionary Force) who had been training in Egypt when the decision to invade Turkey had been taken.

The Naval bombardment of the Straits Forts (9 February – 16 March)
The Naval attempt to force the Straits (18 March)

From <http://www.1914-1918.net/Gallipoli.htm>