Complex sentence: Los Halcones ("The hawks") was a black-op army group that were trained in the United States, created in late 1960s to repress demonstrations and prevent another large popular movement as was the student movement of 1968 to rise again.
Split into simpler sentences: Los Halcones ("The hawks") was a black-ops army group that was trained in the United States. The groups was created in the late 1960s to repress demonstrations and prevent another large popular movement such as the student movement of 1968 to rise again.