Is it permissible to play a war game in which the army speaks German or English, and the game is devoid of fighting Muslims, while the player imagines himself to be engaged in jihad and fighting the enemies of the religion?

Language is not tied to religion, so the issue is not with the language itself, but rather with the faith or identity. If the issue is merely with the language, there is no harm. However, if the language is combined with symbols indicating a false identity or religion (such as crosses), then harm arises. Furthermore, preoccupation with such games is disliked (makrooh).