WASHINGTON — The granddaughter of General Dwight D. Eisenhower thanked those who carried out the D-Day invasion, telling them during a 70th anniversary commemoration Friday at the nation’s World War II Memorial that “the world would have been a very different place” had their campaign failed.

Susan Eisenhower joined Elliot Roosevelt III, the great-grandson of President Franklin D. Roosevelt, representatives of 14 countries, several dozen World War II veterans and hundreds of spectators at the memorial on the National Mall to remember history’s largest amphibious assault.

Dozens of veterans who fought on D-Day were present. Now well into their 80s and 90s, some could still walk without help, though most were in wheelchairs or used canes. A few wore military uniforms.