The Communist Manifesto: The proletariat will gain mass, and strength.

Karl Marx : Political Theorist
Advancements in industrial production will grow the masses of the proletariat, but through their increasing numbers, they will find increasing strength against the bourgeois (the owners of the means of production).
"This call was also visionary. In 1848, the proletariat was only a minority in society in most European countries, not to mention the rest of the world. Today, the mass of wage workers exploited by capital - workers, employees, service workers, temporary workers, agricultural workers – is the majority of the population of the globe. It is by far the main force in the class combat against the world capitalist system, and the axis around which other struggles and other social actors can and should be articulated." - 'The Communist Manifesto 160 years later', Michael Löwy, 2008

Karl Marx, The Communist Manifesto. (1848). Ebook (Progress Publishers, Moscow, 1969).