The Republic of China Air Force (ROCAF) was officially formed by the "Kuomintang" (KMT) after the establishment of the Aviation Ministry in 1920. As tensions mounted between China and Imperial Japan in the 1930s, air units from the Chinese warlords, including those from the Guangdong Provincial Air Force, and overseas Chinese aviators, became integrated into the centralized command of the ROCAF, nominally as the Nationalist Air Force of China, and coordinating with the Second United Front to counter the Imperial Japanese invasion and occupation.