[2] A law establishing the right to collective bargaining had been passed by the Germán Busch government, but the government's perceived shift on labor issues remained untested until the 1942 miners' strike.
[1] Bolivia had formally entered World War II on the side of the Allied Powers after the Japanese attack on Pearl Harbor in December 1941, and the Peñaranda government held that wartime strikes represented an unacceptable disruption of Bolivian production for the United States.
When Siglo XX and Catavi mine workers presented a petition demanding a 100% increase in wages in 1942, management refused to negotiate and the miners' union leaders called for a strike.
[1] When the mine workers proceeded to march toward management offices on 21 December 1942, the Bolivian military surrounded the crowd and fired for six hours.
[1] The massacre resulted in an open rupture in the already deteriorating relations between Peñaranda and the moderate and radical reform parties within the Bolivian Congress.