八一 refers to August 1, 1927 — the date of the
南昌起义 (Nanchang Uprising), when CCP forces under
周恩来,
朱德,
贺龙 and
叶挺 launched the first armed rebellion against the KMT. The PLA counts this as its founding day (
八一建军节). The character
八一 appears on the PLA flag, on military uniforms, and as a prefix for PLA-affiliated institutions:
八一队 (army sports team),
八一厂 (film studio),
八一大楼 (defense ministry HQ).