Why do C languages require parens around a simple condition in an if statement?

Tell me how to interprit the following:

if x ++ b;

Looks silly but...

if( x ) ++b;

or

if( x++ ) b;

or perhaps "x" has an overloaded operator then...

if( x ++ b){;}

Edit:

As Martin York noted "++" has a higher precedence which is why I've had to add the operator overloading tidbit. He's absolutely right when dealing with modern compilers up until you allow for all that overloading goodness which comes with C++.

If there are no brackets around expressions in if constructs, what would be the meaning of the following statement?

if x * x * b = NULL;

Is it

if (x*x)
    (*b) = NULL;

or is it

if (x)
    (*x) * b = NULL;

(of course these are silly examples and don't even work for obvious reasons but you get the point)

TLDR: Brackets are required in C to remove even the possibility of any syntactic ambiguity.