The Industrial Revolution of the 1800's was not a conflict in and of itself, but it did create problems between social classes. This social stratification created the ideological differences between capitalism and socialism which, in turn were the catalyst for a number of wars between the superpowers of the 20th century.
The Industrial Revolution itself was a combination of new inventions and the presence of a huge labor supply caused by a population explosion. The high population was the result of better farming techniques developed during the Agrarian Revolution.
The Industrial Revolution altered every aspect of life for people. People flooded cities in search of work in the growing factories. The results of this were dangerous working conditions, extremely low wages, child labor, women working for less than men, poor housing, poor sanitation, and a widening of the gap between rich and poor. These problems led to a variety of social, economic, and political reforms including the idea of socialism.
Socialism is the concept that the nation should control all aspects of production with the people making all decisions. This is directly opposite of capitalism which promotes competition among individual owners. One version of socialism, called communism, came to the forefront. Karl Marx (seen here) and Friedrich Engels, in the book The Communist Manifesto, believed that history was the story of the class struggle of the lower class against the upper class. Marxism called for the workers of the world, called the proletariat, to rise up and unite against the capitalist, called the bourgeoisie, in bloody revolutions. Marxist socialistic thought was instrumental in the rise of the Soviet Union and China.