Kate Middleton donned a stylish coat as she visited the site of the Battle of the Somme in France Thursday along with Prince William and Prince Harry to honor the worst day in British military history. The Battle of the Somme was fought during World War I by the French and British armies against the German Empire.

Middleton opted to wear a $3,800 black, white and gray zigzag-printed Missoni coat over a black dress for the occasion. She completed her elegant look pairing it with heels, pearl earrings and a black pillbox hat. Prince William and Prince Harry both looked dapper in their navy suits.

The three royals paid tribute to those who lost their lives in the battle that was fought from July 1 to Nov. 18, 1916. Among those killed was Capt. Henry Archibald Cubitt, a 24-year-old member of the Coldstream Guards and the great-uncle of Camilla, the Duchess of Cornwall.

William and Harry both spoke at the service, with William saying that the first day of the battle, on which 19,240 British soldiers were killed, "was in many ways the saddest day in the long story of our nation. ... The gift you gave your country is treasured by every one of us today. The sacrifice you made will never, ever be forgotten."