Short answers, pulled from the story.
Karl Marx published the first volume of Das Kapital in 1867. This work marked a decisive break from classical political economy and emerged as a direct response to Adam Smith's The Wealth of Nations.
Marx defined value as socially necessary labor time invested in producing a commodity. A worker's wage covered only the necessary means of subsistence required to maintain their family and future work capacity while the rest constituted surplus labor pocketed by capitalists as profit.
Friedrich Engels edited the second and third volumes of Das Kapital based on Marx's notes after his death. These unfinished manuscripts were eventually published by Engels to complete the critique of political economy.
Critics alleged that correcting errors meant aggregate price and profit no longer equaled value and surplus value. Ladislaus von Bortkiewicz claimed Marx drew conclusions not following premises in Value and Price in the Marxian System during 1906, 07.
Terms neo-Marxian post-Marxian and radical political economics first appeared in 1970s and 1980s referring distinct tradition stemming from Marxian thought. Leading figures associated with leftist Monthly Review School developed dependency and world systems theories during this period.