It is obvious that federal fiscal deficits will have to be addressed sooner or later in the US, and seeing how difficult it is to raise taxes, one has to think about how to trim expenses. Of course, the biggest line item is defense, and one can ask what the consequences of cutting these military expenses could be. Critics of those cuts will point to WWII, where the military build-up has pulled the US out of the Great Depression. While I do not quite agree with this interpretation of this anecdote, it is worthwhile to study more generally the impact of military expenses.
Giorgio d’Agostino, Paul Dunne and Luca Pieroni do a literature review and note that out should not just look at the direct impact of expenses. Indeed, a military build-up is also more likely to generate conflicts, and after all a conflict is overall a waste of resources as much effort is spent blowing physical and human capital to pieces. The multiplier argument is also rather vacuous, as these funds could be used for other purposes as well with higher multipliers, in particular when you compare wars in foreign lands versus infrastructure at home. The same applies to the argument that military research has some positive impact on civilian technology (why not simply focus research on the latter?).
This clearly makes it difficult to make a case that military expenses are good for growth. Empirical work is really difficult, like so often with cross-country growth regressions, but d'Agostino, Dunne and Pieroni conclude that the evidence tends towards a negative impact. The only ones that obtain positive impacts are those that include supply-side effects, and those are of course rigged to provide a positive impact.