This letter is best known in the abbreviated and partially altered version included under the heading ‘A Single Spark can Start a Prairie Fire’ in the editions of Mao’s writings published at Peking since 1951. It was written at Kut’ien, Fukien Province, where the Ninth Party Congress of the Fourth Red Army had adopted a few days previously Mao’s long and programmatic resolution—part of which is in the Selected Works (Vol. I) as ‘On Correcting Mistaken Ideas in the Party’—on the ideology, style and organization of the Red Army. This meeting, which took place in one of the safer base areas, was the last of a series held over three years in the Fourth Army, the kernel of the Red forces, and has, with justice, been regarded in China during recent decades as an historic ideological rectification movement that set the Maoist style for the Red Army and its successors.