The Christmas song Silent Night has long been a cherished part of our shared culture — in 2011 it was even granted UNESCO cultural heritage status.

But the power of the carol was never so clear as on Christmas Eve 1914, when fighting on the battlefields of World War I stopped - and a lone soldier's exquisite voice made history.

"It was impromptu, no one planned it," Stanley Weintraub, the author of Silent Night: The Story of the World War I Christmas Truce, told Daybreak South's Chris Walker.

"It has to begin with something, and it did begin with elements of shared culture. If it hadn't been for shared culture, certainly there would have been no Christmas truce."

Weintraub said it started with German officer, Walter Kirchhoff, a tenor with the Berlin Opera.

"He came forward and sang Silent Night in German, and then in English. In the clear, cold night of Christmas Eve, his voice carried very far.

"The shooting had stopped and in that silence he sang and the British knew the song and sang back."

Gradually the troops crawled forward into No Man's Land, said Weintraub.

The song had a deep impact on many of the soldiers.

"Soldiers … wrote home the day after to their families, to their wives, and to their parents, saying, 'You won't believe this. It was like a waking dream.'"

"They recognized that on both ends of the rifle, they were the same."

To hear more about the history of Silent Night and the Christmas truce, click the audio labelled: One of the stories of Silent Night.