These veterans still maintain a brotherly bond in peacetime, as they were brothers-in-arms during the war.

brothers 是 brother 的复数形式，意思是"兄弟"。 in-arms 由介词 in 和名词 arms（武器）组成，字面意思是"在武装状态下"。 brothers-in-arms 指"战友"，强调在战争中并肩作战形成的特殊情谊，就像亲兄弟一样。