If you had been in Australia or New Zealand yesterday you would have not been able to miss the activities marking ANZAC Day.
In 1915 Australian and New Zealand soldiers formed part of the Allied expedition that set out to capture the Gallipoli peninsula to open the way to the Black Sea for the Allied navies. The plan was to capture Istanbul, capital of the Ottoman Empire and an ally of Germany. They landed at Gallipoli on 25 April, meeting fierce resistance from the Turkish defenders. What had been planned as a bold strike to knock Turkey out of the war quickly became a stalemate, and the campaign dragged on for eight months. At the end of 1915 the allied forces were evacuated after both sides had suffered heavy casualties and endured great hardships. Over 8,000 Australian and 2,700 New Zealand soldiers died. News of the landing at Gallipoli made a profound impact on Australians at home and 25 April quickly became the day on which Australians remembered the sacrifice of those who had died in war.
Now that you have some background, you can see the day in pictures.