IIRC, The Persians were advancing with a huge army, perhaps 200,000, and Belisarius had only 10,000 to stop them. He took a position on the wing of their advance and sent envoys inviting the Persians to talk. When the Persians arrived they saw a camp completely at ease with no sign of stress and formations marching to and fro. Actually, the formations were the same units walking in and out of the woods over and over, giving the illusion of great numbers, and all troops were ordered to appear relaxed to show confidence.
The Persian envoys returned to their army and reported that they were at a camp which must have been just the main outpost of a much larger army, and the enemy showed no signs of fear at their advance. Given that this "large army" was also on the flank of the Persian advance, the Persians lost their nerve and retreated.
What a move.