Surrealism grew out of the Dada movement, as another movement trying to revolutionize art and to help destroy the vestiges of the world order that created World War 1. Dadaism was very decentralized while Surrealism was a very defined collective group operating out of Paris. You could look at Surrealism as an attempt to direct and consolidate the anarchism of Dadaism into a more coherent revolution against art and society. Surrealism went from 1924 to World War 2.
Surrealism wanted to destroy the rational consciousness that created a culture and world they despised. Surrealism maintained the subconscious was the true realm of artistic creation and the superior reality to any form of conscious and rational thought. Andre Breton, a poet , led the Surrealist movement and stated "in a violent reaction against the impoverishment and sterility of thought processes that resulted from centuries of rationalism, we turned towards the marvelous and advocated it unconditionally." Surrealism through dreams and the subconscious was the purest form of thought without the control and manipulation of rational thought.
Surrealism thought that the hyper real landscape paintings were a realistic depiction of the imagery of dreams. That reality showed the real images of the subconscious mind through dreams. Hyper reality is more honest and not riddled with fraudulent, manipulated gestures of artistic flair which created the banality of the romantic paintings trying to simulate a state of dreamlike quality and reality. The subconscious could be more brutal in it's immediate expression of this hyper reality and at the same time more honest.
Dadaism and Surrealism represented artistic reactions to the corrupted social orders and political movements designed to consolidate the individual to governmental and cultural stranglehold on their artistic aspirations. With the worldwide contemporary movement now towards merging the corporate and state entities into one consolidation of thought and action, Dadaism and Surrealism still represent an artistic and political threat in the form of artistic anarchism and political anarchism.