Western Ukraine was Polish from 1920 to 1939.
(Western Ukraine was Polish from 1920 to 1939.)
I wonder how much percentage was Jewish?
Otherwise, an ungoverned Western Ukraine would almost certainly generate partisan activity and competing Ukrainian governments. As it happened, after the end of WW II, a Ukrainian partisan army led by a renegade SS Colonel and affiliated with Bandera invaded and pillaged what is now the southeast corner of Poland.