There’s a science fiction short story, I think from the 1950s, about a near future when the US is in a war, and all disciplines that do not directly contribute to the war effort are given up, including history. Then soldiers began vanishing. It is discovered that they are escaping into the past, but not the real past. The past they imagine. The leading general is told that only a historian can explain what these strange pasts are, and what is happening. “Then bring me a historian,” the general orders and waits and waits and waits…
Another example of a discipline no one could imagine might be useful is Old Norse. When the US entered WWII, it replaced England as the main occupier of Iceland, an important air and naval base in the North Atlantic. All at once the US needed people who understood the Icelandic language. This is how my father, the son of Icelandic immigrants, got sent to Iceland. In addition to people from immigrant families, the US government recruited Old Norse scholars, since Old Norse is medieval Icelandic and very close to modern Icelandic. A lot of these guys were primarily Anglo-Saxon scholars and spoke Old Norse with a thick Anglo-Saxon accent. They also has problems with vocabulary. My father said it was fun to watch these guys in the dining room of the Hotel Borg in Reykjavik. They knew twenty words for sword, but no phrase for scrambled eggs
Actually you could make up a phrase: the verb to stir (hræra) and the noun egg (egg). In any case, can you think of a discipline more useless in the modern world of 1942 than Old Norse?