WASHINGTON (REUTERS).- An American soldier stands alone amid the long grass of a Vietnamese field accompanied by the helicopter that brought him there while a few other soldiers are seen in the background.

"Landing Zone," a somber depiction of the Vietnam War in 1966 by soldier John Wehrle, is among about 300 paintings by U.S. servicemen and women that will be unveiled to the public for the first time at Philadelphia's National Constitution Center in September.

The paintings have been selected from about 15,000 collected by the U.S. Army since the 1840s. Most have never been on public display.

"Art of the American Soldier" focuses on the duties, sacrifices, and everyday lives of troops, and covers every conflict from the World War One to Afghanistan.

The depiction of war through painting gives it an emotional dimension that photography cannot match, said Col. Peter Crean, deputy director of the Army Center of Military History.

"War is a totally emotional experience, and the medium of painting brings that out in a way that other mediums can't," Crean told reporters at the Pentagon, where the Army's vast collection of paintings has been held, mostly in storage.

In "GI's in Paris", Floyd Davis painted three exhausted-looking soldiers as a shawl-clad woman huddles in the background during the closing stages of the World War Two.

The war in Iraq is depicted by "Big Country", a 2004 painting by Heather Engelhart showing the silhouette of a soldier against a darkening sky.

But the hardship of war is briefly forgotten in "Bob Hope Entertaining the Troops Somewhere in England, 1943" also by Floyd Davis. It shows the comedian wearing a metal helmet and a trench coat, performing in front of laughing soldiers.

The show includes four oil paintings by Master Sgt. Martin Cervantez, a combat artist who spent 90 days in Afghanistan in 2008 recording the experiences of soldiers on active duty.

Cervantez worked from some 18,000 photos but argued that photographic evidence is no substitute for the personal experience of the artist who is also a soldier.

"The public needs to see this because it's from the soldier's perspective," he said.

The exhibition will give visitors a clearer understanding of war at a time when more troops are in Afghanistan fighting the longest war in U.S. history and public support is wavering, said David Eisner, chief executive of the National Constitution Center.

Eisner argued that the center is an appropriate setting for the show because U.S. soldiers take an oath to defend the Constitution, whose stated purpose is to secure liberty for American citizens.

"It's important that we understand that what the soldiers are fighting for is the framework of our democracy," he said.

The exhibition is also designed to enable active and retired servicemen and women to give their relatives a realistic view of their experience of war.

"If a soldier takes his family to the museum, I want them to be able to say, 'That's what it was like,'" Cervantez said.

Other soldiers/artists will be invited to submit their works to an online gallery for possible display in a computer kiosk within the exhibition. The show runs from September 24 to January 10, 2011 and will then tour other U.S. cities.