The underlying cause of the Peasants' Revolt in England during the 14th century was a combination of social, economic, and political factors. The primary catalyst was the economic hardship brought on by the Black Death, which significantly reduced the population and labor force, leading to labor shortages. As a result, peasants demanded higher wages and better working conditions. Additionally, the introduction of the Poll Tax in 1380 further fueled unrest. The revolt, which erupted in 1381, reflected deep-seated grievances against the feudal system and the oppressive actions of local lords and government authorities, ultimately highlighting the struggles between social classes during that period.