The Sand Shield is an automatic defense jutsu unique to Gaara. Its the main part of his Ultimate Defense, along with the Sand Armor. Being infused with his chakra allows Gaara to control it with his mind and use it for combat purposes as well. This sand is also infused by the will of Gaara's mother, Karura, to protect him from harm when she died, this being the reason why its an automatic defense that protects him regardless of his will. The defense has always been very formidable in speed and strength, but in part 2 of Naruto had massively improved in these ways, as in part 1, the Sand Shield could be outran by incredibly fast attacks or brocken through by highly powerful strikes, sucha s the Chidori, whereas in part 2 nothing and no one other than Madara Uchiha has even come close to doing the same. Things like the Susanoo's sword, the Amaterasu, and the Steam Imp jutsu of the Second Mizukage are such examples.