You need more than stimulated emission for a laser. I think that figuring out how to create a population inversion in an excited state is the best candidate for the inception point of the laser as a specific possibility, and I believe the honor for that achievement goes to Townes circa 1950.

Nothing is ever simple. Before Townes' 1951 population inversion, there's also Kastler's 1950 invention of optical pumping, and Dennis Gabor's 1947 invention of holography (yes, 1947, before lasers, which stimulated development of lasers)

https://en.wikipedia.org/wiki/Optical_pumping

https://en.wikipedia.org/wiki/Dennis_Gabor

Interesting. On following up on your links, I see that while optical pumping was invented first, Townes was able to make the first maser by using an electric field to separate out an excited state of ammonia, achieving a population inversion without pumping. http://home.fnal.gov/~kubik/FermilabWebsiteDocs/Masers.ppt

The closer you look, the less the history of innovation looks like a simple sequence.