After returning to Shanxi, Yan placed Bo in charge of his "Patriotic Sacrifice League", a local organization dedicated to organizing local resistance against Japanese invasion[1] (which Bo organized as a front for promoting Communism).[5] While working under Yan, Bo organized a "dare-to-die" corps of young volunteers[3] and used his good relationship with Yan to persuade Yan to release communists that he was holding in prison.[5] After the Japanese succeeded in taking northern Shanxi in 1937 and wiping out 90% of Yan's military forces,[6] Bo collected the survivors of his unit and conducted anti-Japanese guerrilla operations in southern Shanxi.