Soldiers from New Zealand, Australia, UK, France, India and Newfoundland, battled harsh conditions for eight months as Ottoman forces fought for their homeland.
More than 130,000 men had died - at least 87,000 Ottoman soldiers and 44,000 Allied soldiers including 2779 New Zealanders.
The Chunuk Bair ceremony was the last attended by Prince Charles and Prince Harry, the site of bitter hand-to-hand combat by New Zealand forces. Mr Foss read the last letter of Lieutenant-Colonel William Malone.
While his family weren't aware of their WWI connection, they are of Mr Foss' brush with royalty.
"My mum is over the moon that I met the Royals," Mr Foss said.