What happened during the Normandy landings?

Troops from the 48th Royal Marines disembark on Juno Beach during the D-Day landings on June 6, 1944.

London (CNN)Donald Trump joined Queen Elizabeth II and 15 other heads of state in the British city of Portsmouth Wednesday to commemorate the 75th anniversary of D-Day; the largest joint military operation ever undertaken.

World leaders, royalty and veterans gathered at the Portsmouth Naval Memorial to mark the Normandy landings, which were the starting point for the liberation of Nazi-occupied Europe during World War II.