UPA-West was established in December 1943 as one of the UPA's three operational groups, alongside UPA-South [uk] and UPA-North.
A fourth operational group, UPA-East [uk], was planned but never realised.
At lower levels, the transition from the UNS to UPA-West took until March 1944.
[2] UPA-West grew to become one of the largest and most effective groups of the UPA (in particular, the 4th Military District),[1][3] and the operational group was assisted logistically by the OUN, which provided food and weaponry and organised recruitment efforts.
[4] However, with the gradual decline of the UPA insurgency, it would be eventually cease to function in 1949,[1] and Vasyl Sydor (UPA-West's commander since 1947) was killed in combat with the NKVD.