In January 1933 , to secure Manchukuo 's southern borders , a joint Japanese and Manchukuo force invaded Rehe , and after conquering that province by March , drove the remaining Chinese armies in the northeast beyond the Great Wall into Hebei Province .
In January 1933 , to guard Manchukuo 's southern borders , a joint Japanese and Manchukuo force invaded Rehe , and after conquering that province by March , drove the remaining Chinese armies in the northeast outside the Great Wall into Hebei Province .