shield is projected from Endor to the Death Star orbiting it. The Executor has shields, without which
it is very vulnerable to attack; concerted bombardment by the Rebel
fleet could bring these down without much difficulty.
Several critical events during the Battle of Endor display critical weaknesses in Imperial armor against physical impact.
Two logs smash an AT-ST handily, and a rogue A-Wing smashes straight through the forward bridge window of the Executor. The Super Star Destroyer's command center was destroyed, and the ship plummeted to its doom, crashing nose-first into the second Death Star. A Y-Wing is also seen impacting an ISD, although without great consequence for the ISD. It is possible that the shields of the ISD were up during that impact.
Empirical armor penetration formulae show penetration depth is related to a term that ranges from V2M/A to VM1/2/A1/4, where V is the velocity, M is the mass, and A the area of impact. As the armoring plates' thickness would seem to be substantially lower than the caliber of the large impacting projectiles, the first formula is strongly suggested.
The logs, however, condemn the AT-ST. Granted, the AT-ST's armor was not actually penetrated; however, while it is possible that the AT-ST may resist some small arms fire, it is clearly not a heavily armored vehicle.
Log smashes AT-ST.