Replies in underlined bold. I think you're confusing libertarian for minarchist.
I'm not confusing libertarian for minarchist. You and others who are not comprehending what I am saying are confusing libertarian for something other than minarchist. A libertarian would be a subset of minarchist, should any other types of minarchist (not motivated by preservation of liberty) actually exist.
Let's make this simple.
If you are a libertarian you are a minarchist.
If you are an anarchist you are not a libertarian.
If you are a libertarian you are not an anarchist.
Why anarchists are so dissatisfied with being called anarchists is beyond me; you believe it, you should own it. Regardless, what you are not allowed to do is redefine a very distinct and different term to shoehorn it into your belief system because it has more positive connotations than the correct word for your beliefs.
A libertarian is someone who believes the fundamental principle expressed in the Declaration of Independence: that government should exist for the sole purpose of protection of liberty - and should have no other role. NOT that government shouldn't exist at all. Yes this requires a monopoly on the lawful use of violence within a defined territory (which is the definition of sovereignty). This is the "necessary evil" part of the libertarian description of government.
What makes it necessary is that this arrangement provides for maximum human liberty, far more than the every-man-for-himself anarchist approach, where the only liberty you really have is your natural right to violence. Which will make for a bloody affair, by the way, as everyone else will also have theirs as well, and if you understand human beings at all you know they will use it liberally and without conscience.
If you believe government should not exist at all, there is a perfectly good word already available for you to use: "anarchist". It literally means absence of government, and if that's what you believe in, that's what you are.
Also, "individual sovereignty" is the same thing as anarchism, it's just a more complicated way to say it.