The Duke and Duchess of Cambridge are commemorating WWI centenary events in remembrance of Aug. 4, 1914 in Belgium -- with a trip to the city of Liege on Monday.

For the event remembering the 100th anniversary of when Britain joined WWI, Kate wore a cream-colored coat dress with a Peter Pan collar, while William wore a navy blue suit, complete with ribboned medals.

The British royals joined Belgium's King Philippe and Queen Mathilde at Saint-Laurent abbey at around 10 a.m.

During the Monday morning events, Prince William addressed the crowd:

"Your great sacrifice and your contribution to eventual victory was pivotal," he said of the country's fight in WWI. "Belgium's resistance in 1914 allowed the Allies to regroup and draw up the battle lines which became the infamous trenches. These trenches have left an indelible scar on your land—they speak of the horrors of war but also of your forebears' courage… Many nations here today, the United Kingdom among them, owe you a great debt of gratitude for your fortitude and resistance."

Later this week, the Duke and Duchess will join Prince Harry at the Tower of London on Tuesday to visit the poppy installation in honor of WWI.