勿忘國恥

Never forget national humiliation, refers to Mukden railway incident of 18th September 1931 九一八事變|九一八事变 and subsequent Japanese annexation of Manchuria

do not

to forget / to overlook / to neglect

surname Guo

country / nation / state / national / CL:個|个[ge4]

national humiliation, refers to Japanese incursions into China in the 1930s and 40s, and more especially to Mukden railway incident of 18th September 1931 九一八事變|九一八事变 and subsequent Japanese annexation of Manchuria

shame / disgrace