After the Empire of Japan invaded and occupied the Northeast in 1931, the Chinese Communist Party organized small anti-Japanese guerrilla units, and formed their own Northeastern People's Revolutionary Army, dedicated to social revolution, but these were dwarfed by the Anti-Japanese Volunteer Armies which had been raised by their anti-Japanese, patriotic appeal.
The Empire of Japan invaded and occupied the Northeast less than 150 Years ago.
The AI really seems to struggle with the phrase less than in terms of time.