Conditions on the peninsula were by any standard appalling. The men were ill-equipped due to the expectation that they would have advanced off the beach quickly and supplies were difficult to land and slow coming. Nutrition was poor - largely bully beef (tinned salt beef), hard tack biscuits, sometimes supplemented by bacon, onion, jam and cheese. With water in short supply, hygiene was also poor with no water to spare for washing clothing resulting in lice infestations. The only chance to wash personally was by swimming - inherently dangerous because the beach was periodically under fire. Sanitation was rudimentary and rotting bodies, refuse tips and open latrines provided excellent breeding grounds for flies which carried diseases like dysentery, diarrhoea, enteric fever and para-typhoid. Illness accounted for many of the casualties during the campaign.
It was decided to withdraw from the peninsula in December, 1915 after the deaths of 44,070 allied troops (including 8,709 Australians) and 86,692 Ottoman troops and vast numbers of injured on both sides. In a brilliantly organised evacuation all allied troops were withdrawn without losses. An elaborate plan made it appear as if normal camp life was continuing while troops were gradually evacuated mainly at night between 8 December and 18 December, 1915. Various ingenious devices like the drip or "pop off" self firing rifle were cobbled together by the troops and used to make the Ottoman troops think they were still under fire.
In Australia the Gallipoli campaign has become a symbol of Australia's growth into nationhood and it is commemorated with dawn ceremonies and marches of those who have served in the armed forces and their descendants. So many Australians wanted to visit Gallipoli this year to attend Anzac Day ceremonies that there has had to be a ballot. Enmity long forgotten, the Turkish people also visit the war cemeteries and welcome visitors whose ancestors they were once involved in deadly combat with. I'd hope that we would be as generous in the same circumstances.
I'm somewhat ambivalent about what Anzac Day has become because it seems to me that many people have a somewhat romanticised view of the young hero at war when the reality is anything but that. The truth is war is brutal and destructive and, even after the conflict is over, the survivors often live on damaged mentally and physically. That said I still see Anzac Day and similar commemorations like Remembrance Day on 11 November as important. They remind us of the terrible waste of life that war entails on all sides and that is something that every generation needs to have reinforced.
You can read more about the Gallipoli campaign here and about World War 1 in general on this website which has a fairly comprehensive list of total casualties (killed or injured) for all countries involved in World War 1 - at least as far as they can be determined given many were never recorded and so their fate still remains unknown. It usefully shows the percentage of casualties of those mobilised from each country, too.
"Lest we forget."