Hyperinflation is a completely different issue from inflation, and it's kind of odd for it to become the monetarist bugaboo. When the US has a massive war debt payable immediately, or a complete economic collapse that the government decides to cope with by price controls, then you'll see hyperinflation. But then, hyperinflation will be the least of your problems.

Inflation in the 70s (chart): https://inflationdata.com/articles/wp-content/uploads/2014/0...

To the data: I agree that there are fluctuations there. But average inflation for the decade of the 1960s was 2.45%. For the 1950s, it was 1.82%. The inflation rate even for 1972 was above the average rate for the 1950s and 1960s. 1976, the bottom of the next trough, was higher than 1972. And then you look at 1974 and 1979, in the context of the 1950s and 1960s, and yes, it sure does look like inflation is increasing. Yes, there are decreases (business cycle), but each cycle is higher than the last one.

Then, In Friedman's book inflation is related to the amount of money in circulation, yet since the 80s the amount of money and inflation have almost zero correlation in the US. Some of Friedman's concepts were useful to reach that point, but still: we now have been living for 40 years in a world where Friedman's model is unable to explain anything.

Certainly the central bank can create as much inflation as it wants, by simply printing and distributing more money (which usually takes the form of the central bank buying assets such as bonds with the new money). There's no limit to the ability of the central bank to make the currency valueless.

In the other direction, they can usually increase the value of money (ie, create deflation) by reducing the money supply, but it is possible that at some point the public might simply stop regarding the government's money as being worth anything. The only thing that might stop that is that people would still need government money to pay taxes.

Did you actually mean it the other way around as in they can create money by buying govt bonds/treasury bills/etc and retire them by selling them back to the market.

Not quite true. Every bank can print money (well, the modern day equivalent of increasing a digital number somewhere), and does so when they make loans.