Australian prime minister Tony Abbott and his New Zealand counterpart John Key are among the host of dignitaries attending a two-day programme of commemorative events in Istanbul and on the Gallipoli peninsula. Prince Charles, Prince Harry, Irish president Michael Higgins and Turkish president Tayyip Erdogan are also among those leading the ceremonies.

At least 45,000 allied soldiers lost their lives during the ill-fated nine-month campaign to take the peninsula and knock Ottoman Turkey out of the war. A further 86,000 Turkish troops died, and an additional 300,000 troops from both sides are thought to have been wounded.

Addressing an international ceremony at Abide, on the Gallipoli peninsula, Prince Charles spoke of a “shared duty” to overcome tolerance and fight prejudice “so we can say we have honoured the sacrifice of all those who have fought and died here on the battlefield at Gallipoli and elsewhere.”

The 100th anniversary adds a special poignancy to this year’s Anzac Day commemorations on April 25. Australia and New Zealand’s annual day of remembrance pays tribute to those from both countries who have served and died in wars, conflicts and peacekeeping duties, plus the contribution and suffering of all those who have served.

Anzac Day was originally held specifically to honour the contribution of members of the Australian and New Zealand Army Corps who fought for the Allies against the Ottoman Turks during the Gallipoli campaign. The peninsula has become a site of pilgrimage for visitors who travel halfway around the world to visit the graves of their nations’ fallen on Anzac Day.

Prime minister Abbott, speaking ahead of the centenary, described Gallipoli as “the crucible in which our national identity was forged.” He added: “But it left horrific scars. It was, in a critical sense, our nation’s baptism of fire – and 8000 Australians didn’t come back.”

The Gallipoli campaign – badly planned and poorly executed – was intended to open up the Dardanelles straits to allied shipping and lead to the capture of Constantinople – present-day Istanbul. But the 50-mile-long Gallipoli peninsula was heavily fortified, and the invading troops came under deadly fire from the moment they hit the beach at dawn on April 25, 1915.

The allies’ death toll over the next nine months is estimated at 25,000 British and Irish soldiers – including some Canadian troops who fought with the British army – 10,000 Anzac troops, and 10,000 French troops. Few ever made it much further than a few hundred metres from the shore. The war council in London finally accepted the inevitable when it withdrew the Anzac troops in December 1915, with the remaining British soldiers leaving in January 1916.