>>4117
Delaying action. They needed to keep the Imperials busy long enough to get their transports out. It was basically a matter of keeping the Imperial focus off the transports and on them.
Their gun emplacements are old and outdated, but still effective against a fair amount of Imperial Vehicles. They were just unfortunate that the Imperials were able to get their AT-AT's through (they lost a few of them to the terrain before the battle).