I read somewhere that, "That the war of Gog and Magog will be an internal, spiritual war, when everyone will have to battle to remain strong with his emunah, but it will not be a war fought with guns and weapons."
Is there any sefer that says this?
My guess is that this is something based upon Chovot haLevavot, in Shaar Yichud haMaaseh §5, where Bahya ibn Paquda describes the "real" battle in one's life as being against an internal enemy, rather than against external forces (link). This story is also related by R' Yishaya Horowitz (Shnei Luchot haBrit II: Parshat Korach), and so the version you heard may also be based upon a commentary to that text. You can read his version here, about eight lines up from the bottom of the left-hand column.