Over 100,000 Revolutionary Guards and Basij volunteer forces charged towards the Iraqi lines. The Iraqi troops had entrenched themselves in formidable defences, and had set up a network of bunkers and artillery positions. The Basij used human waves, and were even used to bodily clear the Iraqi minefields and allow the Revolutionary Guards to advance. Combatants came so close to one another that Iranians were able to board Iraqi tanks and throw grenades inside the hulls. By the eighth day, the Iranians had gained inside Iraq and had taken several causeways. Iran's Revolutionary Guards also used the T-55 tanks they had captured in earlier battles.