To Europeans, Britons, Canadians, and Americans, stories of World War I often focus on the great battles of the Western Front like the Somme, Ypres, Verdun, Vimy Ridge. But to Australians, New Zealanders, and Turks the first thought that comes to mind is probably Gallipoli.
The Gallipoli Campaign (April 1915-December, 1915) was the British and Allies' attempt to capture the Dardanelles (the straights leading from Sea of Marmara and Istanbul to the Mediterranean) and eventually march on Istanbul, forcing the surrender of the Ottoman Empire and gaining control of the Black Sea beyond.
It is widely viewed that this campaign was mismanaged and suffered from a lack of commitment to from the start. The most successful operation of the campaign, in fact, was the evacuation.