Sentence:  But it is also true that Braque was the consistent pioneer in the use of simulated textures as well as of typography ; and moreover , he had already <WSD>begun</WSD> to broaden and simplify the facet-planes of Analytical Cubism as far back as the end of 1910 . 
Meaning of the word marked with <WSD> tags:  take the first step or steps in carrying out an action