Make iTunes Treat my iPhone Like A New Phone I want to backup my phone as if it were a new phone.  Context that makes my situation different from other similar questions I found:


I've deleted all my old backups
I do not have my old backup password
So I cannot change my password to a new one (this requires the old password)
And I cannot uncheck "Encrypt iPhone backup"


That is, all my old backups are gone, and my "old password" is effectively useless -- I have no need for it anymore.  I want iTunes to treat my phone as if were brand new, and allow me to setup a new Encrypt backup password, and make a fresh backup as if for the first time.

How can I get iTunes / my phone into this state?

EDIT

Please note I believe this is not a duplicate of Create backup iPhone with forgotten encryption password.  At the very least, the answers there do not answer my question.

From the accepted answer:


  The short answer is no. The phone thinks you are a thief trying to steal the data and won't cooperate with attempts to initiate a second backup. 


It makes sense that you would need a password to restore a password-protected phone.  I am not trying to do that.  I am trying to backup a phone that I have access to as if it were fresh.  Why should passwords I used to protect previous, now-deleted backups have anything to do with this goal?  How would preventing me from backing up my phone in any way prevent theft?  What if I lost my laptop --
 how would this phone be treated on a brand new laptop?  Would I also not be able to back it up there?

From the other answer:


  if you have no problem deleting your backup this "problem" is a breeze! head over to iTunes, then open up the preferences, klick on devises, then select your phone, and delete the backup!
  ...
  when backup deleted simply create a new backup from scratch :)


I have already deleted my old backups.  I still cannot create a new backup from scratch with a fresh password.
Once you have selected that you want to encrypt the backup of an iPhone, it is not possible to uncheck without the password, or by erasing the content of the iPhone.
The information about the encryption status is saved on the iPhone, not in iTunes, so erasing all your backups wont do much in this situation.

This may seem weird to many people, but it's basically a safety measure.
Let's assume that someone broke in to your house and got away with both your computer and iPhone, got access to the computer because you had no Filevault enabled, and now wanted to move your data from your iPhone to your computer, and would be able to do so, just by erasing your old backups first. This would be somewhat of a security flaw in my opinion.

So to say it short, you need to erase your iPhone to disable the encrypted backup setting, if you do not know the password.