South African Cover To The Sun Motor Company, Elkhart, In.

I agree that the Great War (it was not called World War 1 at the time since there was no expectation that there would be a World War 2 afterwards) likely did not have much impact on auto companies. Rather it was a time when everyone who had an idea and a few thousand dollars could and did start a car building company. Over the period from the start to the late 1920s there was a great deal of companies starting and failing, and one company buying out another company. This continued in a lesser way during the 1930s through the 1950s. The reason most companies failed was they were out produced and out marketed by the handful of companies that had the most savvy managers. Ford was the first big winner with their Model T and later Model A built on an assembly line in huge numbers for very low cost making them affordable for most anyone, and designed to be serviced easily with standardized spare parts readily available across the country. In the 1920s Chevrolet became the big competitor to Ford. Other companies were smaller but aimed at more niche markets such as Chrysler, Cadillac. Oldsmobile and Dodge for example.

I am not sure how this affects the arguments being made about the effect of WWI on the automobile industry, but it couldn't have hurt to be one of the companies selected to build the Liberty L-12 engine. The contract was split between Buick, Ford, Cadillac, Lincoln, Marmon, and Packard-Bell. Well, maybe it didn't help Marmon so much.

A small clarification…. Cadillac was the first one to suggest, and implement, the concept of standardized parts. Ford introduced mating 'simple parts' with standardizing the processes on the assembly line itself.

And despite the urban legend, Model Ts came in chassis color other than black including a red and a green. The urban legend states that Ford used only black because it was the quickest drying paint. While this was true, another time issue was the cost of switching over to a different color on the line. But Ford was willing to deliver non-black Model Ts if the customer was willing to pay for them when they first introduced them and also towards the end of the production run. (There was a middle period when black was indeed the only color offered.)

I concur that the political astuteness was also an important factor in the history of auto manufacturers. Being able to win military contracts and establish relationships (such as Studebaker's B-17 aircraft engines) greatly impacted how they fared through the lean war years. This was critical so that they were poised to take advantage of the post war marketplaces.
Don