My emphasis.But on February 1, 1808, Junot decreed the extinction of the power of the House of Braganza in Portugal, ripping out, once and for all, the agreements of Fontainebleau. This decree confirmed to the Spanish authorities the bad faith of Napoleon, who continued to send armies to Spain, supposedly in transit to assist Junot in Portugal, but who were allowed to stay in northern Spain, taking several cities.
It's interesting to note that the other monarchs in Austria, Russia, England, etc, all felt the same way about this (N's bad faith) as did the "Spanish authorities." It was just Spain's turn to finally come to the same hard realization concerning the character of the man.
It's actually understandable why N didn't see any real potential problems in seizing the ancient monarchies of Portugal and Spain; after all, seizing territory/states, overturning local authority, often by military means and converting them into something "French," is what he had been doing for some time.
If there is any one identifiable date that is the tipping point of when the arch of N's meteoric rise began it's fall, perhaps it is February 1, 1808: the extinction, by N's degree, of the power of the House of Braganza in Portugal.