Although Dr. Sun Yat-sen was established in Nanking as provisional president, the expeditionary force was needed to put down the warlords who controlled the north and unify the country.
原來當時國父雖赴南京就任臨時大總統，組成臨時政府，但北方依然為軍閥所據、袁世凱主張君主立憲。