SCOTT SIMON, HOST:
This is a new version of a very old song.
(SOUNDBITE OF SONG, "PACK UP YOUR TROUBLES IN YOUR OLD KIT-BAG")
UNIDENTIFIED MAN #1: (Singing) Pack up your troubles in your old kit-bag and smile, smile, smile.
SIMON: "Pack Up Your Troubles In Your Old Kit-Bag" sent a lot of lads of to The Great War, which began a hundred years ago this summer. We now call that World War I. A British military charity, called SSAFA, has enlisted active and former service members, their families and British celebrities to record a new version.
(SOUNDBITE OF SONG, "PACK YOUR TROUBLES IN YOUR OLD KIT-BAG")
UNIDENTIFIED PEOPLE: (Singing) What's the use of worrying? It never was worthwhile. So pack up your troubles in your old kit-bag and smile, smile, smile.
SIMON: What's the story behind the song?
AUBREY POWELL: My name's Aubrey Powell. I'm the grandson of Felix Powell, who wrote the famous war song "Pack Up Your Troubles In Your Old Kit-Bag."
SIMON: Along with his brother George, who wrote the lyrics in 1915.
POWELL: In those days, the most important thing was to have a song that would give encouragement to the troops as they went into battle - something that they could sing and march to and give them inspiration.
SIMON: So when a music publisher held a war song-writing contest, they entered "Pack Up Your Troubles."
POWELL: They first performed it in South Hampton in England, and suddenly the audience just started singing along with them. And they suddenly realized that what they previously considered as a bit of a dud - they got a hit on their hands.
(SOUNDBITE OF SONG, ""PACK UP YOUR TROUBLES IN YOUR OLD KIT-BAG")
UNIDENTIFIED MAN #2: (Singing). Pack up your troubles in your old kit-bag and smile, smile, smile.
POWELL: They started in the music halls and it went to the trenches.
SIMON: There wasn't iTunes or YouTube to make a song a hit back then. It went from soldier to soldier.
POWELL: I mean, it spread like wildfire through the trenches. Within a few months, every soldier knew it. The Germans were singing it. And their trenches were only 200 yards away. And they'd sing it in German. The English would sing it in English together.
(SOUNDBITE OF SONG, "PACK UP YOUR TROUBLES IN YOUR OLD KIT-BAG")
UNIDENTIFIED PEOPLE: (Singing) Pack up your troubles in your old kit-bag and smile, smile, smile.
POWELL: Soldiers could easily march to it and sing it. And it uplifted their spirits. They felt great about life in absolute abject misery.
SIMON: But Felix Powell struggled with misery.
POWELL: Things went very bad for him financially and also just personally. And in 1942 after the start of the Second World War, things got too much for him, and he'd left a suicide note saying I cannot write music anymore.
SIMON: The new version sung by young British soldiers, sailors and airmen, old veterans standing ram-rod straight, families and a ukulele.
(SOUNDBITE OF SONG, "PACK UP YOUR TROUBLES IN YOUR OLD KIT-BAG")
UNIDENTIFIED PEOPLE: (Singing) Pack up your troubles in your old kit-bag and smile, smile, smile. Transcript provided by NPR, Copyright NPR.