In which country did cubism first start as an movement?

Georges Braques and Picasso developed Cubism in a couple of forms, Analytical Cubism and Synthetic Cubism. Braque and Picasso exchanged paintings daily, signing them on the back or not at all as they developed a new way of looking. Picasso changed his way of representing form of canvas when he saw an African sculpture that was taken from the Louvre. He went to a painting he had started, "Les Demoiselles D'Avignon" and modified, incorporating elements of the mask into his work, to the extent that his collectors thought he had gone mad!

Braque's family were decorators so he incorporated some wallpaper from the family business. Before that Picasso and Braque had used a subdued neutral palette, using black, white and a brown, sepia color, the two men were first in using the 2 dimensional support in a new way, flattening out the space as had Cezanne, a great influence on several of the artists from this period in the early years of the 20th C.

They worked in Paris.