"We do not destroy our enemies,we change them" What are the means by which Big Brother achieves this?

Think about what is more
useful.

Fight and kill an enemy or just let him become an
ally that shares and believes in the idea or ideal that you are going to promote as "the
best" of the possible worlds?

The enemy of the Big Brother
is the individual thought. If every book is rewritten and history has changed, thoughts
are rewritten too.

If every newspaper or broadcast on tv is
saying just the same thing and discuss an argument in the same way, nobody would have
another opinion, so there is no enemy to fear about.

Fear
against fear is one of the most powerful way to control our
opinions.

Julia is betrayed by Winston's most terrifying
fear.