1. Strict auditing system: The China government has a strict auditing system for films and other literary and artistic works, which needs to be checked at different levels.

2. Sensitive historical themes: War of Resistance against Japanese Aggression is an important period in the history of China, but films involving the national army's anti-Japanese war may involve some sensitive topics, such as ethnic cooperation and the anti-Japanese national United front, which need to be handled with caution.

3. Difficulty in shooting: The film reflecting the national army's anti-Japanese war needs to dig deep into historical events and people, but at present, there are relatively few materials and research results about this period of history in China, which makes it difficult to shoot.

4. High investment risk: The film reflecting the national army's resistance to Japan may involve some war scenes and historical figures, and political, military and cultural factors need to be considered, so the investment risk is high.

In a word, there are many reasons for the lack of domestic films reflecting the national army's resistance to Japan, which need to be analyzed and discussed from many angles.