? movie; shields reflecting sunlight; enemy falling into ravine.

I'm looking for the name of a movie that was shown on AMC perhaps within the past 6 months or so.
It was similar to these movies and I remember seeing it at the drive-in back in the early to mid 1960's.
The scene I recall most vividly was right at sunrise, the two armies were facing each other at a distance. The enemy were charging on their horses and chariots while the good guys were lined up, not moving.
Suddenly, the stationary guys aimed their shields to reflect the sunlight right into the faces of the charging enemy. While blinded, they fell into what seemed like a narrow version of the Grand Canyon.
At the time I checked out the name of the movie here and it seemed that the movie was not yet released into DVD.
Can anyone share the name of this movie?