With some strategic changes by António Spínola in the late 1960s, the Portuguese forces gained momentum and, taking the offensive, became a much more effective force. Between 1968 and 1972, the Portuguese forces took control of the situation and sometimes carried attacks against the PAIGC positions. At this time the Portuguese forces were also adopting subversive means to counter the insurgents, attacking the political structure of the nationalist movement. This strategy culminated in the assassination of Amílcar Cabral in January 1973. Nonetheless, the PAIGC continued to fight back and pushed the Portuguese forces to the limit. This became even more visible after PAIGC received anti-aircraft weapons provided by the Soviets, especially the SA-7 rocket launchers, thus undermining the Portuguese air superiority.