Merchet joined Libération in the 90s, where he works on Defence topics. Since July 2007, he has publish a professional blog, Secret Défense. He left Libération after the summer of 2010 and joined Marianne.
He is an auditor at the Institut des hautes études de défense nationale (49th session).
- Les Commandos Marine, co-authored with Marie Babey (photos), France Delory, Paris, 1999
- Caroline Aigle, vol brisé, Jacob-Duvernet, Paris, 2007
- Mourir pour l'Afghanistan, Jacob-Duvernet, Paris, 2008
- Défense européenne, la grande illusion, Larousse, coll. "À dire vrai", Paris, 2009
- (French) Secret Défense at Libération (14 July 2007 - 29 October 2010)
- (French) Secret Défense at Marianne (29 October 2010 - 5 June 2013)
- (French) Secret Défense at L'Opinion (from 5 June 2013)