have something/someone by the tail

[drdeng]

What does "have something/someone by the tail" mean, as is used in the following passage from Irwin Shaw's Bread Upon the Waters?

"...My ideas... well, that nothing is permanent. Those old Romans, they thought they had the world by the tail, they lorded it over everybody and went around telling people how wonderful they were and thought they were doing the poor dopes in other countries a big favor by making them Roman citizens and ever..."

[Quizmonster]

In the example you give, it clearly means that they believed they were in control. The more usual version means exactly the opposite! That is, the phrase about "having a tiger by the tail". As long as you can hold onto the tiger's tail, it can't get hold of you with its teeth, but...how long can you hold on? The instant you let go, it'll have you. So, that version means you are really in a very tricky situation and only seem to be in control.