Which "ism" found itself on the decline with the introduction of the peasant foot soldier ap euro?

The correct answer is Feudalism.

Explanation:

Feudalism refers to the system of economy/government which existed between the ninth and fifteenth century in Europe. It saw an economic system where Landlords, in exchange for farming the land and giving security to the peasants, allowed the plebians to live on their land.

Lets I forget, it is important to note that during this time (which predates the Hundred Years' Battle) the loyalty of the peasants was sole to the Landlords. However, as the peasants fought battle after battle, during the war which took about 100 years between 1337 to 1453, the peasants who were formerly unskilled in military affairs become seasoned soldiers who were more committed to the affairs of the state. After the war, the remaining landowners required the services of farmers and soldiers. This according to the annals of history contributed to the factors which eroded the feudal system and put a lot of power on the formerly powerless plebians.

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c. wright mills's sociological imagination suggest investigating to explain this increase?