Aragorn, Legoles, and Eomer fight valiently atop the wall in an attempt to hinder the orcs from gaining the wall.  The army of Saruman storms in through a culvert that the was aparently made by devilry.  They are armed with spears and not as well armored as the men that guard Helm's Deep.  Though the Orcs out number Theoden's army 10 to 1, this little skirmish at the wall was not successful for the Orcs on this attempt.
 
 

This image has been taken from the Atlas of Middle Earth, written by Karen Wynn Fonstad

Helm's Deep is a fortress of stone that looms around the Glittering caves of Aglarond.  Rohan had in all about 3800 soldiers, and only about 2700 of them that actually fought in this battle.  There were many huorns in this battle also, but they did not come till later.  Saruman's army was vast, and much larger then that of Rohan's, but here is an example of how a well fortified encampment can make all the differance.

In the upper right portion of the map, you see a overhead view of the battle.  The host of Saruman attacks at many spots, each of them countered by Rohan.  By attacking at around ten differant locations they spread their forces out, but also cause their enemy, which in this case is Rohan, to spread out.  Rohan's army is already weaker in number, and now spreading them apart to defend so much of the wall thins out the defense.  Aragorn, Gimli, and Eomer are in the very top of the map fighting where there the assault is at its hottest.  There are battering rams, and great numbers of orcs.  You can look at the key on the upper right portion of this map, to follow the battle and see the strategy in which Rohan used to counter the onslaught of Isenguard.

In the bottom half of the map you can see the final strategy used by Rohan to destroy the army of Saruman.  Theoden rode out of Hornburg, with Aragorn and Eomer at his side.  They had little hope of victory at this point, for they did not foresee help only moments away.  The Orcs fled before the rage of Theoden and his riders, but as they fled the army of Erkenbrand led by Gandalf the white came suddenly at them.  Gandalf had been away and collected Erkenbrand's infantry.  The army of Isenguard was now in dissary, with no where to turn to.  As they fled away from both Erkenbrand's Infantry and Theoden's riders, they found themselves in a wood of Huorns.  Not one Orc was spared, and those of the wild men that survived, were pardoned if they pledged never to attack Rohan, and to help mend what they damaged.