operations while the OUN was in charge of administrative duties; each had its own chain of command. The six main departments were military, political, security service, mobilization, supply, and the Ukrainian Red Cross. Despite the division between the UPA and the OUN, there was overlap between their posts and the local OUN and UPA leaders were frequently the same person. Organizational methods were borrowed and adapted from the German, Polish and Soviet military, while UPA units based their training on a modified Red Army field unit manual. The General Staff, formed at the end of 1943 consisted of operations, intelligence, training, logistics, personnel and political education departments. UPA's largest units, Kurins, consisting of 500-700 soldiers, were equivalent to battalions in a regular army, and its smallest units, Riys (literally bee swarm), with eight to ten soldiers, were equivalent to squads. Occasionally, and particularly in Volyn, during some operations three or more Kurins would unite and form a Zahin or Brigade. UPA's leaders were: Vasyl Ivakhiv (Spring – 13 of May 1943), Dmytro Klyachkivsky, Roman Shukhevych (January 1944 until 1950) and finally Vasyl Kuk. In November 1943, the UPA adopted a new structure, creating a Main Military Headquarters and three areas (group) commands: UPA-West, UPA-North and UPA-South. Three military schools for low-level command staff were also established. In terms of UPA soldiers' social background, 60 percent were peasants of low to moderate means, 20 to 25 percent were from the working class (primarily from the rural lumber and food industries), and 15 percent were members of the intelligentsia (students, urban professionals). The latter group provided a large portion of the UPA's military trainers and officer corps. The number of UPA fighters varied. A German Abwehr report from November 1943 estimated that the UPA had 20,000 soldiers other estimates at that time placed the number at 40,000. By the summer of 1944, estimates of UPA membership varied from 25,000 to 30,000 fighters up to 100,000 or even 200,000 soldiers. Structure The Ukrainian Insurgent Army was structured into four units: UPA-NorthRegions: Volhynia, Polissia. Military District "Turiv"Commander – Maj. Rudyj.Squads: "Bohun", "Pomsta Polissja", "Nalyvajko". Military District "Zahrava"Commander – Ptashka (Sylvester Zatovkanjuk).Squads: "Konovaletsj", "Enej", "Dubovyj", "Oleh". Military District " Volhynia-South"Commander – Bereza.Squads: "Kruk", "H.". UPA-WestRegions: Halychyna, Bukovina, Zakarpattia, Zakerzonia. Military District "Lysonja"Commander – Maj. Hrim, V.Kurins: "Holodnojarci", "Burlaky", "Lisovyky", "Rubachi", "Bujni", "Holky". Military District "Hoverlja"Commander – Maj. Stepovyj (from 1945 – Major Hmara).Kurins: "Bukovynsjkyj", "Peremoha",