Thousands attended the ceremony (Picture: PA).
Veterans, serving personnel and members of the public were among those to attend.
The service carried extra importance this year as it marked 100 years since the end of the First World War.
The Great War claimed the lives of 5 million soldiers from 30 countries, including at least 750,000 British soldiers.
The service was held in front of the Armed Forces Memorial.
Remembering those who gave their lives, the Reverend Tim Flowers, Assistant Chaplain of the arboretum, said theirs had been a sacrifice for future generations "that all people may together live in freedom, justice and peace".
After the act of remembrance by the Chaplain, Rev Vic Van Den Bergh, addressed the crowd and said:
"We will remember them."
A two-minute silence was held as five buglers from the Royal Marines played The Last Post.
The Duke and Duchess of Gloucester laid wreaths at the memorial, where many had already been left with personal tributes.
Among the tributes, wooden crosses, and poppy wreaths, there was a simple painted stone which read: "1918-2018, 100 years - George Parker, thank you."
Another wreath was for Private Harry Grocott from Shawbury in Shropshire.
As a 16-years-old, he died serving with the King's Shropshire Light Infantry, after his dug-out was hit by a German shell in April 1916.
A card fixed to the poppies, read:
"We never knew you but we know of you - we will never forget your selfless sacrifice. Thank you."