Why doclasses come into conflict, according to Marx?

Accordingto Karl Marx, the groups with similar interests and common objectivesform same classes. This formation of classes is based on a historicalprocess, which means that in every society class, identity among thepeople was present. With the change in modes of production,technology and social relations, these classes became antagonist toeach other, thus resulting in class conflict. For instance, in acapitalist society, there is a conflict between the capitalists andthe working class. In such a society, both of them are in a directopposition to each other and hence the class conflict arises betweenclasses.