In older papers, one sometimes finds references to sources of funding directly linked to or overseen by military agencies. For example, I have memories of seeing acknowledgments to DARPA funding in a pure mathematics article - much to my surprise, as it didn't seem to have any relevant applications. (However, I haven't been able to track down said paper in my personal collection, nor indeed any which contain said references; this might suggest that such support was rare even in the past.)

In more recent papers - at least those I encounter - such attributions are conspicuously absent. Instead those written at American institutions overwhelmingly thank NSF grants for their support.

Question. Is my impression accurate? Namely, did the US military fund pure research with little real-world upshot in the past; and has it become more reticent in recent years? If yes, when and for what reason did this shift occur?

• I would be interested in a historical explanation just as much as a personal account.
• To be sure it is only natural that the defense sector still has a keen interest in certain parts of mathematics, say cryptography or data science. I am specifically interested in (past and present) support for projects where the payoffs seem far-fetched.