Zhang Tengyue reads a letter of Liu Bojian, an early founder of the Communist Party of China. [Photo provided to China Daily]

Zhang Zixuan, the program's chief editor who led the selection of letters from more than 10,000 entries, has read many wills and death-bed letters.

He said the crew selected the letters from online resources or handwritten copies, and the team discovered that military officers and soldiers regularly wrote final letters before big battles.

"China's mainstream education actually avoids talking about death, with such clues seen clearly in ancient school texts influenced by Confucius philosophy. It values the meaning of life and urges people to optimistically strive for this life," Zhang said.

Most Chinese would not prepare for death even after being seriously ill for long, he said.

"But wartime is an exceptional time and probably creates the largest number of wills in every era," he said.

"Warriors were ordered to write the last letters to their families. And the survivors would write other 'last letters' for the next battle if they didn't die in the last."