Chen Gu felt somewhat tempted. He initially hadn't wanted to reveal himself, worried his cover would be blown. A high school student suddenly turning into a "tactical master" would inevitably arouse suspicion from certain people. Moreover, given the "complicated" experiences of his original body, it would be difficult to avoid issues.
However, now the military had shown sufficient sincerity. The real reason Chen Gu began to seriously consider the offer was... his older son's dream of becoming a general.
Chen Gu only knew that Chen Jixian wanted to be a general from what his grandson, Chen Zili, had told him. He was merely "aware" of this dream and, subjectively, didn't place much importance on it. After all, if you're in the military, you can't exactly say to others, "I don't want to be a general," right?