Who was the former Dadaist who wrote the Manifest of Surrealism?

I believe the correct answer is André Breton.

André Breton was a French writer and poet, who admired Tristan Tzara (one of the founders of the Dadaism movement) and Dadaism for a long time. But he became disillusioned by the apathy of the Dadaists and slowly started to transit from Dadaism and to Surrealism. His completely separated from Dadaism when he published "Surrealist Manifesto" ("Manifeste du surrealism") in 1924.