When a square is attacked (i.e. not a 'quiet' square), don't do a regular search of x more moves, but use a simple swap algorithm.
The swap algorithm involves: using a negamax algorithm for the counter-attacks and ignoring if the following attacking moves are valid (e.g. produce check), and even allow for x-ray attacks. Excellent example here: http://chessprogramming.wikispaces.com/SEE+-+The+Swap+Algorithm
When a square is attacked (i.e. not a 'quiet' square), don't do a regular search of x more moves, but use a simple swap algorithm.
The swap algorithm involves: using a negamax algorithm for the counter-attacks and ignoring if the following attacking moves are valid (e.g. produce check), and even allow for x-ray attacks. Excellent example here: http://chessprogramming.wikispaces.com/SEE+-+The+Swap+Algorithm