25 April is Anzac day in Australia and New Zealand. This day remembers the day that the Australian & New Zealand Army Corps (ANZAC) landed at Gallipoli in Turkey in 1915.
The landing was part of an ambitious Allied attempt to capture Istanbul, defeat the Turkish Ottoman Empire (allied with Germany), and open up a supply route to Russia. Troops from Britain, Ireland, France, Canada, & India were also involved.
The Anzacs distinguished themselves in this ultimately futile action (at places like Anzac Cove, Suvla Bay & Lone Pine), and their actions had a powerful impact on the newly-independent Australia, and the soon-to-be independent New Zealand.
During eight months of stalemate, the Gallipoli campaign incurred 500,000 troops killed or wounded from all sides. Most of the Allied troops were redeployed to the Western Front.
To this day, Anzac Day remains the most important day when Australians and New Zealanders remember their war dead.
The Turkish general at Gallipoli was Mustafa Kemal (known as Atatürk), who would later become the first President of Turkey.
The Gallipoli campaign was the brainchild of Winston Churchill. The failure of the campaign ultimately led to Churchill being sacked, ended the career of British General Sir Ian Hamilton, and helped bring down the government of British Prime Minister Asquith. The lessons were learned, however, and influenced the planning of the D-Day landings in 1944 and the Falkland Island landings in 1982.