When 10-year-old Liu Jian was studying at a Beijing primary school in the early 1960s, his teacher read a famous poem written by Chairman Mao Zedong to the class.

But when the students were confused about the battle depicted in the poem, the teacher asked Liu if he could get details from his grandfather.

Liu is the grandson of Zhu De, one of the founding fathers of New China and the People's Liberation Army.