– A century after the United States joined its allies in the muddy trenches of Europe in a war unlike one the world had endured before, a Kansas City ceremony Thursday recalled the tragedy and heroism of the time.

Under clear skies and chilled air, a crowd gathered at the National World War I Museum and Memorial to mark the sacrifices, military and civilian, of a now-gone generation.

Dignitaries from 30-some nations joined Americans at the foot of the Liberty Memorial amid period music and military pomp and circumstance. Cannons fired. Music played. Military re-enactors gathered in period dress.

Helen Patton, whose grandfather George S. Patton led a tank squadron through France in World War I, was there. So were descendants of Gen. John Pershing, of Sgt. Alvin York, and of one of the bilingual Signal Corps switchboard operators known as the "Hello Girls."

Patton talked about her grandfather honoring the first four American war deaths in France. "He gathered strength from their sacrifices," she said, and taught others to "never underestimate how much it means to hold a soldier in your heart."

She read a poem and, a cappella, sang about the yearning of those at home who worried about soldiers at war. "It's the spirit of the match that pulls you through … but at home she's waiting."

A band played the songs of the branches of the service, watched short films recalling the human cost of the war and listened to speeches about U.S. troops crossing the Atlantic in defense of democracy.

"Today, we honor a generation of Americans no longer among us physically, but we can all sense their presence … a century later," said Charles E. Schmidt, the national commander of the American Legion. "Their success in the Great War … laid a foundation not only for the American military, but for America itself."

A century after April 6, 1917, the Kansas City gathering observed the world's introduction to the carnage of modern warfare. Soldiers began the war on horseback and ended it in armored vehicles.

"We still live in the long shadow of World War I in every aspect of our lives," said Rob Dalessandro, chairman of the World War I Centennial Commission.