As of 1 June 1989, the International Institute for Strategic Studies estimated that the Army comprised four corps and 12 division headquarters. The IISS noted that these formations 'were in name only; below establishment in units, men, and equipment. Brigades were of battalion size.' Units and formations listed in 1990 within six military sectors included the twelve divisions, four tank brigades, 45 mechanized and infantry brigades, 4 commando brigades, one surface-to-air missile brigade, three field artillery brigades, 30 field battalions ["sic": probably field artillery battalions], and one air defence artillery battalion. The armed forces declined in size from a possible high of 65,000 in early 1990 to about 10,000 later that year, due to desertions and battlefield defeats.