The British World War I campaign against the Dardanelles was initially meant to be purely a naval effort, but its failure to force a passage through Turkey's defenses required a change of strategy. The new plan was to adopt a peripheral campaign to secure the Gallipoli Peninsula. If the originally planned 24 April 1915 landing was successful, land troops could clear away the Turkish shore emplacements and field artillery, and thus permit the passage of the British fleet to Constantinople. Coincidentally, on 24 April 1915 Turkey began to purge its Armenian minority in anticipation that as fellow Christians the Armenians might back the British against the Turks. Eventually, as many as a million Armenians died as a result of this Turkish repression.

General Sir Ian Hamilton, who was commander of Eastern Command, was in charge of the Gallipoli operation. He had serious doubts that a landing operation could succeed, and was warned that the Turks might fortify the coast, turning the operation into a “second Crimea,” just like a similar landing disaster some 60 years earlier in the Crimean war. Nevertheless, when Kitchener ordered the landing to be attempted, Hamilton decided that the Anzac force would land to the north of Gaba Tepe and the 29th Division would land at five beaches near Cape Helles. While the 29th went north, the Anzacs would advance east across the peninsula to block Turkish reinforcements.

This plan was too complicated. By simultaneously landing at six different beaches, Hamilton hoped to confuse the Turkish defenses. But instead the landing parties quickly got bogged down. Rather than move immediately inland, the two forces landing at Helles Y and S beaches awaited the arrival of the main force from the south. Meanwhile, further to the north, the Anzac landing was just north of Gaba Tepe. Hamilton's mistake of not leaving the beaches immediately to attack the Turkish troops was to have dire consequences.

Among his many problems, Hamilton completely underestimated the Turkish response. In mid-March 1915, they formed a new Fifth Army commanded by General Liman von Sanders, former head of the German military mission to Turkey. Soon, the Turks had moved about 40,000 men and 100 artillery pieces to the west side of the peninsula ready to oppose the landing.