Pls broad my knowledge on this

(1) Who among the army, navy and air force is the most powerful (in terms of ranking)?

who get the most destructive weapons?

And who will win if they face each-other?

(2) I learnt USA army said then that "Nigerian army is too strong to face in ground battle"

Fast forward to today where Nigerian Soldiers reportedly run from BokoHaram, can American Army fear Nigerian army in ground battle again?