ANZAC Day marks the anniversary of the first major military action fought by Australian and New Zealand forces during the First World War and is a major national observance in both nations.

It marks the anniversary of the first bloody battle on the shores of Gallipoli - the first campaign that led to major casualties for the Australian and New Zealand Army Corps during World War I - and commemorates all the conflicts that followed.

When war broke out in Europe in August 1914, Australian and New Zealand soldiers formed part of the expedition that set out to capture the Gallipoli peninsula in Turkey in order to open the Dardanelles to the allied navies.

The ultimate objective was to capture Constantinople (now Istanbul since 1923), the capital of the Ottoman Empire, an ally of Germany.

The Australian and New Zealand forces landed on Gallipoli on April 25th, meeting fierce resistance from the Ottoman Turkish defenders. What had been planned as a stroke to knock Turkey out of the war became a stalemate, and the campaign dragged on for eight months.

At the end of 1915, the allied forces were evacuated from the peninsula, with both sides having suffered heavy casualties and endured great hardships.

The Gallipoli campaign had a profound impact on Australians and New Zealanders at home, and April 25th soon became the day on which both nations remembered the sacrifice of those who died in the war.

Although the Gallipoli campaign failed in its military objectives, the Australian and New Zealand actions during the campaign left a powerful legacy and became an important part of the identity of both nations.

Each year, Australia and New Zealand conduct three commemorative services at Gallipoli: a joint Dawn Service at the ANZAC Commemorative Site, followed by an Australian Memorial Service at Lone Pine, and a New Zealand Memorial Service at Chunuk Bair.  This year, the prime ministers of Australia and New Zealand will be joined at Gallipoli by British royals Prince Charles and Prince Harry.

An exhibit at the Pentagon opened April 22, 2015 representing over 100 years of common support in conflict by the armed forces of Australia, New Zealand and the United States. The "Aussies", the "Kiwis" and the "Yanks" are depicted in 250 feet of murals and military memorabilia in the hallway, providing a visual history of the many operations in which our troops have fought side-by-side, such as World War II, Korea, and Vietnam. The timeline begins in 1908 with President Teddy Roosevelt sending the U.S. Great White Fleet to Sydney Harbor in Australia and Auckland Harbor in New Zealand as a show of unity and purpose in the Pacific region.