The Chinese communist party became a peasant revolutionary party after the spectacular destruction of the urban basis of the movement by Chiang Kai-shek in Shanghai in 1927. But who and what was a peasant, and how did this group become a revolutionary group?
In one sense the answer is obvious. China's population consisted of a majority of poor farmers at the time of the collapse of the Qing dynasty, under a variety of forms of land tenure. They were poor, had little land, and were subject to exploitation by landlords, lenders, and the state. So we might say that this answers both questions: peasants were poor farmers, they were a large majority throughout China, and they were potentially revolutionary as a result of their poverty and exploitation. All that was needed was a party that could mobilize and activate them.
This response is too simple, however, for several reasons. First, the concept of peasant is a social and political construction. A "farmer" is an agricultural producer; but this fact about production status tells us little about how rural people defined their own social realities or the way that others defined them.
Second, the mobilization of "peasants" along class lines requires an organized political effort by a party that aggressively makes for the salience of class over other affinities -- kinship, lineage, regional identity, or ethnicity. Marx expressed his assessment of the lack of solidarity of the French peasantry of the 1840s in these terms: "A small-holding, a peasant and his family; alongside them another small-holding, another peasant and another family. A few score of these make up a village, and a few score of villages make up a Department. In this way, the great mass of the French nation is formed by simple addition of homologous magnitudes, much as potatoes in a sack form a sack of potatoes" (Marx, The Eighteenth Brumaire of Louis Bonaparte). In order for a population to become a self-conscious identity group, it is necessary for a deliberate process of identity-formation to take place. The CCP worked single-mindedly to create this affinity with class identity throughout the 1920-30s in rural China. (Lucien Bianco, Peasants Without the Party: Grass-Root Movements in Twentieth-Century China; Odoric Wou, Mobilizing the Masses: Building Revolution in Henan.)
And third, it turns out that the politically defined status of "peasant" incorporated its own definition of internal inequality -- between rich, middle, and poor peasants. These terms of internal differentiation played a prominent role in the mobilization strategies and policies of the CCP in its drive to revolution. The CCP emphasized conflicts within the class of peasants as much as the conflicts between peasants and others.
The mobilization strategies of the CCP of the 1930s were aimed at creating a large and energized supporting population of poor and middle peasants. They pursued this goal by recruiting local cadres who could communicate the party message to their intended supporters and by offering a program of land reform and social reversal that would strongly appeal to this group. Their efforts were successful in several important base areas, and the CCP was in fact able to cultivate a loyal base among poor and middle peasants. Moreover, this group increasingly provided recruits for middle and higher positions of leadership in the military and political organizations of the party.
So we might say that the peasant movement was in fact created and shaped by CCP doctrines in the 1930s as a contingent but portentious social force in China. And for the first 30 years of the Chinese communist state serious efforts were made to retain the loyalties of this social segment.