前仆後繼

one falls, the next follows (idiom); stepping into the breach to replace fallen comrades / advancing wave upon wave

front / forward / ahead / first / top (followed by a number) / future / ago / before / BC (e.g. 前293年) / former / formerly

to fall forward / to fall prostrate

servant

back / behind / rear / afterwards / after / later / post-

to continue / to follow after / to go on with / to succeed / to inherit / then / afterwards