Tests =)

Expected: undefined, instead got: 'A'

The order of the function parameters is fine. I updated one paragraph to match the function specifications (see below), but I don't think the ordering elsewhere needs to change.

Reversed order in that paragraph to match the specifics of the function. Didn't change the ordering anywhere else.

Replaced instances of calvary with knight.

Added random tests to C and NASM.

Your battle resolution matrix is confusing. Put the column and row headers in the same order, and better clarify that it's a defenders vs attackers matrix.

Also, your parameters are out of order. You say it takes attacking and defending pieces, but the function takes defending and attacking pieces (which again, makes the resolution matrix confusing because you have it structured as defending vs attacking)