During the day, the guns were obscured by the heat mirage off the desert. To the advancing British tanks, it seemed as if they were being shot up by invisible guns at near point blank range. Had the British gotten close enough, they would have easily overrun the unprotected German guns and their crews and taken the pass.
I am also played A-H civil war games. Terrain is critical when making decisions during battle.. Make a mistake and you can lose an entire regiment real quick.