I'll answer that first with a resounding "NO" an LLC is not necessary. I owned 3 rentals for 20 years and never had an LLC. Never had a problem.
Of course, an LLC is safer than renting out property in my name and has some additional benefits such as tax write-offs for any improvements/repairs needed.
Can't imagine where you got that idea. It's 100% wrong. As an individual you get the same tax write-offs for improvements, repairs, depreciation and expenses.
Take a look at IRS Schedule E and you'll see what I mean.
https://www.irs.gov/pub/irs-pdf/f1040se.pdf
Here's a couple of IRS publications that will seriously contribute to your education:
https://www.irs.gov/pub/irs-pdf/p527.pdf
You should also be studying the CA landlord tenant guide and statutes:
CA Codes (civ:1940-1954.1)
http://www.dca.ca.gov/publications/landlordbook/catenant.pdf
As for personal liability you can add landlord's liability coverage in increments of a million to your property insurance. Once you start renting out your home you will have to replace your homeowners policy with a landlord's policy. Your insurance agent can handle that.
I would caution you to avoid buying any more rentals and just keep to renting out the home that you can't live in while on active duty.
Take it from me, being an absentee landlord is a high risk proposition, not so much from a personal liability standpoint, but from a lose lots of money standpoint. There will be times when the property is unrented (expenses going out, nothing coming in) when the property is at risk of vandalism and other damage, and there will be tenants that stiff you on rent where you will have to go to court to evict them.
Bottom line, forget the LLC, won't do you a bit of good. Buy the proper insurance and know the laws backward and forward.
You wouldn't go into combat without intel about the enemy and plenty of ammo. Don't become a landlord without intel and ammo or you'll end up financially bloodied.