The Upper Hand Meaning

Example : 1855, Washington Irving, "Guests from Gibbet Island":  There was no refusing him, for he had got the complete upper hand of the community, and the peaceful burghers all stood in awe of him.1883, Robert Louis Stevenson, Treasure Island, ch. 23:  [C]uriosity began to get the upper hand, and I determined I should have one look through the cabin window.1911, Joseph Conrad, Under Western Eyes, ch. 1:  There it was Razumov who had the upper hand, in a composed sense of his own superiority.2003, Christine Gorman, "Playing Chicken With Our Antibiotics," Time, 14 Feb.:  And because they live everywhere and reproduce quickly, bacteria have the upper hand.