Subjugate
SUBJUGATE, verb transitive [Latin Sub and jugo, to yoke. See Yoke.] To subdue and bring under the yoke of power or dominion; to conquer by force and compel to submit to the government or absolute control of another.
He subjugated a king, and called him his vassal.
[Subjugate differs from subject only in implying a reduction to a more tyrannical or arbitrary sway; but they are often used as synonymous.]