Gao Yang didn't know what the enemy was up to, as they clearly had the advantage. All they needed to do was send the tanks into the artillery position; even with just two tanks, they could have caused significant damage to the artillery. Yet, they just gave up the advantage they had hardly gained.
The behavior of the enemy was very strange.
Avoiding the tank's charge route, they lay on the ground, and as long as they weren't hit by the machine guns on the tanks, they considered themselves to have escaped the ordeal. Gao Yang and his men lay on the ground, helplessly watching as the tanks withdrew back the way they had come.
Gao Yang's analysis concluded that after losing a tank and two armored vehicles, the enemy must have felt unable to bear such losses and therefore abandoned the attack. From the enemy's perspective, they wouldn't know how many anti-tank missiles the Skull Gang had; assuming that the Skull Gang still had anti-tank missiles was normal thinking.