the direct command of the General Staff, who serves as its de facto commander. The Vietnam Strategic Rear Forces is also a part of the Ground Force. Arms Military regions The following military regions are under the direct control of the General Staff and the Ministry of Defence: Hanoi Capital City Special High Command (Bộ Tư lệnh Thủ đô Hà Nội): special command tasked for the defense of the Hanoi Capital Region. Headquarters: Hanoi 1st Military Region (Quân khu 1): responsible for the North East of Vietnam. Headquarters: Thái Nguyên 2nd Military Region (Quân khu 2): responsible for the North West of Vietnam. Headquarters: Việt Trì, Phú Thọ 3rd Military Region (Quân khu 3): responsible for the defense of the Red River Delta (except Hanoi Capital Region). Headquarters: Hai Phong 4th Military Region (Quân khu 4): responsible for North Central Vietnam. Headquarters: Vinh, Nghệ An 5th Military Region (Quân khu 5): responsible for South Central Vietnam including the Central Highlands and Southern Central coastal provinces. Headquarters: Da Nang 7th Military Region (Quân khu 7): responsible for Southeast Vietnam. Headquarters: Ho Chi Minh City 9th Military Region (Quân khu 9): responsible for the Mekong Delta. Headquarters: Cần Thơ Main force The Main Force of the PAVN consists of combat ready troops, as well as support units such as educational institutions for logistics, officer training, and technical training. In 1991, Conboy et al. stated that the PAVN Ground Force had four 'Strategic Army Corps' in the early 1990s, numbering 1–4, from north to south. 1st Corps, located in the Red River Delta region, consisted of the 308th (one of the six original 'Steel and Iron' divisions) and 312th Divisions, and the 309th Infantry Regiment. The other three corps, 2 SAC, 3 SAC, and 4 SAC, were further south, with 4th Corps, in Southern Vietnam, consisting of two former LASV divisions, the 7th and 9th. From 2014 to 2016, the IISS Military Balance attributed the Vietnamese ground forces with an estimated 412,000 personnel. Formations, according to the IISS, include 8 military regions, 4 corps headquarters, 1 special forces airborne brigade, 6 armoured brigades and 3 armoured regiments, two mechanised infantry divisions, and 23 active infantry divisions plus another 9 reserve ones. Combat support formations include 13 artillery brigades and one artillery regiment, 11 air defence brigades, 10 engineers brigades, 1 electronic warfare unit, 3 signals brigades and 2 signals regiment. Combat service support