Antonym of RELINQUISH

Relinquish : voluntarily cease to keep or claim; give up.
Withdraw : remove or take away (something) from a particular place or position.
Attack : take aggressive military action against (a place or enemy forces) with weapons or armed force.
Assume : take or begin to have (power or responsibility).
Conquer : overcome and take control of (a place or people) by military force.

Antonym of Relinquish is Assume