I clicked Start Incursion before I had any military units and the error message that came up was not in English even thought that is my chosen language.
Hey! Thank you so much for letting me know! Good catch on the translation issue. There is definitely a bug with the incursions right now, and that specific error message slipped through in Spanish by mistake. I'm working on a fix for both things and it should be updated soon. I'll let you know as soon as it's resolved!