It was nicknamed the "First Army Under Heaven" during the Chinese Civil War and played a significant role during the Sino-Japanese War (1937-1945), where it inflicted substantial casualties on the Imperial Japanese Army.

Formed from the X Force, particularly the New 38th Division, the New 1st Army was among the top five Nationalist crack units.

[1] However, after some time, Sun was dismissed as commander after offending important members of the KMT, including his superior, Chiang Kai-shek's favorite Lieutenant-General Du Yuming.

[citation needed] This dealt a huge blow to the New 1st Army and it began to suffer heavy losses.

[citation needed] Due to this army's group uneasy history with both the KMT and Chinese Communist Party, its successes are rarely talked about across both mainland China and Taiwan.