LSJὀπισθο-φύλαξGlossone who guards the rear :ὀπισθο-φύλαξ [ῠ],ᾰκος,ὁ,A. one who guards the rear : οἱ ὀ. the rearguard,ib. 4.1.6 , Ph. 2.121 , etc.References4.1.6Ph. 2.121