The Duchess of Cambridge was cheered by thousands of people as she took the salute for the first time at Beating Retreat.
More than 750 soldiers wearing ceremonial uniforms stepped out for the annual display at London's Horse Guards Parade.
Kate was hailed by about 7,500 bystanders as she arrived and took her seat.
Wearing a cream collared jacket, with her hair in a slick chignon, Kate smiled and spoke with soldiers who welcomed her to the event.
It paid tribute to the 75th anniversary of D-Day by including a composition taken from The Longest Day, a 1962 film depicting the Normandy landings on June 6, 1944.
Kate was the only member of the royal family to attend the event, with the Duke of Cambridge marking the anniversary at an event in Staffordshire earlier on Thursday.
The hour-long programme featured traditional military anthems telling the history of regiments in the British Army.
Dame Kelly Holmes, Honorary Colonel of the Royal Armoured Corps Training Regiment, took the salute at the event's first night on Wednesday.
Beating Retreat is performed in front of St James's Park across two evenings every year in the week preceding Trooping the Colour, the Queen's official birthday parade.
Additional reporting by Press Association.
