Group photo of the First Corps of the Red Army when they successfully arrived in northern Shaanxi in 1935. [File photo/Xinhua]

During wartime, the collected materials were unable to be reserved, so the itineraries we resort to today are mainly from the detachments of the First Corps as well as diaries of survivors such as Chen Bojun, Tong Xiaopeng and Xiao Feng.

Despite the incomplete statistics and partial documentation, the available materials prove that the First Corp had marched at least 18,000 li, which is also referred in Edgar Snow's well-known book, The Red Star over China.