higher ground
/ˌhʌɪə ˈɡraʊnd/noun
1Ground which is more elevated in relation to the surrounding area.
2 Figurative and in figurative contexts, especially with reference to a position of advantage or superiority in a debate, moral issue, etc.
Origin
Mid 16th century; earliest use found in Richard Morison (c1510–1556), humanist and diplomat. From higher + ground.