The word(s) "mastery" appears 2 time(s) in 2 verse(s) in Quran in Mohsin Khan translation.

(1) Those (hypocrites) who wait and watch about you; if you gain a victory from Allah, they say: "Were we not with you?" But if the disbelievers gain a success, they say (to them): "Did we not gain mastery over you and did we not protect you from the believers?" Allah will judge between you (all) on the Day of Resurrection. And never will Allah grant to the disbelievers a way (to triumph) over the believers.

(2) So if you gain the mastery over them in war, punish them severely in order to disperse those who are behind them, so that they may learn a lesson.