At the same time as Operation Karbala 5, Iran also launched Operation Karbala-6 against the Iraqis in Qasr-e Shirin in central Iran to prevent the Iraqis from rapidly transferring units down to defend against the Karbala-5 attack. The attack was carried out by Basij infantry and the Revolutionary Guard's 31st "Ashura" and the Army's 77th "Khorasan" armored divisions. The Basij attacked the Iraqi lines, forcing the Iraqi infantry to retreat. An Iraqi armored counter-attack surrounded the Basij in a pincer movement, but the Iranian tank divisions attacked, breaking the encirclement. The Iranian attack was finally stopped by mass Iraqi chemical weapons attacks.