How does Zaroff in "The Most Dangerous Game" succeed in getting people to play his game?

Basically, Zaroff gets people to play the game by forcing
them to do it.  He makes it so that playing is the best option that the people
have.

So how could this be?  How could your best option be
to run off and try to hide while some guy comes to hunt you and kill you if he catches
you?  Well, it is the best option if your other option is that you will die for sure and
die for sure in a more painful way.

So what Zaroff tells
them is that if they do not let him hunt them, he will give them to Ivan and Ivan will
kill them in terrible ways.  Here is the quote that shows
this:

"Oh,"
said the general, "I give him his option, of course. He need not play that game if he
doesn't wish to. If he does not wish to hunt, I turn him over to Ivan. Ivan once had the
honor of serving as official knouter to the Great White Czar, and he has his own ideas
of sport. Invariably, Mr. Rainsford, invariably they choose the
hunt."