The battle took place between April 25, 1915 and Jan. 9, 1916.
Britain and France wanted to secure their ally Russia, as the Gallipoli peninsula provides a sea route to what was then the Russian Empire.
Their aim was to capture the capital of the Ottoman Empire, Istanbul.
Turks repelled a naval attack, and there were many casualties on both sides during the eight-month offensive.
When the land campaign also failed, the invading forces withdrew.
Victory against the Allied forces boosted the morale of the Turkish side, which then went on to wage a war of independence in 1919-1922, and eventually formed a republic in 1923 from the ashes of the old empire.
