Dennis was actually the first stagnation theorist I read, at about the age of eighteen, due to a recommendation from Walter Grinder. His strength is to tie stagnationist claims into the political economy of war. This is from 1940 (book link here), I hope it is no longer relevant:
The importance of clearly understanding the dynamic and purely unmoral function of change cannot be exaggerated at a time like this when the major problem is stagnation. America’s problem of unemployment could be solved by rebuilding America or going to war with Japan. The war with Japan is more likely. Why? The answer is that our social philosophy recognizes a need for national defense but not for social dynamism.
…stagnation in any culture is far more normal or usual than what we have been accustomed to think of as progress.
I found this interesting:
A civilization must exalt a tradition of heroism. This it may do in war or pyramid building. Liberalism never glorified heroism in theory but, in its frontier empire-building days, it exemplified heroism in its practice.
You can read Dennis as an extension of the Henry George model, except he is more bullish about population growth and adds the variable of war. In the George model, there are increasing returns and so city life becomes crowded and the scarce factor of land captures the social surplus. Think San Francisco or Singapore. Dennis assumes diminishing returns, and so the frontier is usually more potent than the city, if only a frontier can be kept open and alive. But that is hard to do because it runs against the natural desire of so many human beings for stasis, and thus capitalism tends to evolve into a kind of socialistic fascism.
Dennis, by the way, had an interesting life. Unlike most “alt right” writers, he was half black, but his skin was pale so he was able to pass for white. (In fact he started life as a child preacher, touring the south, accompanied by his African-American mother.) He spent some of his energies trying to convince his “fellow travelers” to support civil rights for blacks, but without much success, and he also was desperately afraid of being unmasked.
Early in his career, he was accepted into mainstream American intellectual life and hung out with elites, rising to the top through the State Department and Wall Street. As the 1930s passed, he became more extreme and the center became more hostile to fascist and semi-fascist ideas, especially if bundled with tolerance for potentially hostile foreign powers. His career had a long downward trajectory, and during World War II he was tried for sedition, though he got off and later died in obscurity, after a final gig as a critic of the Cold War. Gerald Horne wrote a very interesting biography of Dennis.