and 500,000 soldiers in theater, organized into 51 divisions, including eight Republican Guard divisions. Republican Guard units normally received the newest equipment; for example, most of the estimated 1,000 T-72 tanks in the Iraqi Army on the eve of the war were in Republican Guard divisions. The Iraqi Army in the Kuwaiti Theater of Operations (KTO) also included nine heavy divisions, composed mostly of professional soldiers, but with weapons of a generally lesser grade than those issued to the Republican Guard. Most non-Republican Guard armored units had older tank designs, mainly the T-55 or its Chinese equivalents, the Type 59 and Type 69. The remaining 34 divisions were composed of poorly trained conscripts. These divisions were deployed to channel the Coalition's forces through a number of break points along the front, allowing the Iraqi Army's heavy divisions and the Republican Guard units to isolate them and counterattack. However, the Iraqis left their western flank open, failing to account for tactics made possible by the Global Positioning System and other new technologies. In Saudi Arabia, the Coalition originally deployed over 200,000 soldiers, 750 aircraft and 1,200 tanks. This quickly grew to 3,600 tanks and over 600,000 personnel, of whom over 500,000 were from the United States. Iraqi forces Earmarked for the offensive into Saudi Arabia was the Iraqi Third Corps, the 1st Mechanized Division from Fourth Corps and a number of commando units. Third Corps, commanded by Major General Salah Aboud Mahmoud (who would also command the overall offensive), had the 3rd Armored Division and 5th Mechanized Division, as well as a number of infantry divisions. Fourth Corps' commander was Major General Ayad Khalil Zaki. The 3rd Armored Division had a number of T-72 tanks, the only non-Republican Guard force to have them, while the other armored battalions had T-62s and T-55s, a few of which had an Iraqi appliqué armor similar to the Soviet bulging armor also known as "brow" laminate armor or BDD. During the battle of Khafji, these upgraded T-55s survived impacts from MILAN anti-tank missiles. These divisions also had armored personnel vehicles such as the BMP-1, scout vehicles such as the BRDM-2, and several types of artillery. Also deployed along this portion of the front, though not chosen to participate in the invasion, were five infantry divisions that were under orders to remain in their defensive positions along the border. U.S. Marine Corps reconnaissance estimated that the