The idea that analysis must precede synthesis is old, of course. Galileo Galilei and René Descartes already thought it was necessary to distinguish between an analytic and a synthetic step in dealing with any problem.
Langlois/Seignobos talk about this in their text Introduction aux études historiques (1879) as well, focusing especially on the analysis portion to have a solid base of historical information from which to build and create a synthesis.