Why was the city of nanjing extremely vulnerable to japanese attack? ?

The city of Nanjing was extremely vulnerable to Japanese attacks because Chinese political and military leader Chiang Kai-shek and General Chen Cheng withdraw from the city of Nanjing along with elite Chinese troops under heavy and constant bombardment by the Japanese Imperial Air Force . Thus the city was totally unprotected and totally vulnerable to the Japanese attack.

it granted civil rights to african americans.

a stronger government