Originally posted by: RoccondilRinon
The impression I always got was that the shield was like a flat surface above the base; it protected the base from an aerial bombardment but it was possible to sneak under the edges at near-ground-level (ie. with walkers or speeders).
The impression I always got was that the shield was like a flat surface above the base; it protected the base from an aerial bombardment but it was possible to sneak under the edges at near-ground-level (ie. with walkers or speeders).
This is also the way I've always thought of it ever since I was a kid... the shield is aerial, to prevent bombardment from above. I never assumed it went all the way to the ground (thinking so is just the result of seeing the lame Gungan energy shield from Episode I). And as for why the AT-ATs were used, as General Veers explains to Vader:
"My lord, the fleet has moved out of light-speed. Com-Scan has detected an energy field protecting an area around the sixth planet of the Hoth system. The field is strong enough to deflect any bombardment."
Therefore, the Empire had to land beyond the reach of the shield and destroy it from the ground in order to allow the remaining Imperial forces (including Vader) to get to the base quickly.