The legal movement of patriotic and progressive forces had developed since the early 1960s, much ahead of the revolutionary armed struggle which started in 1969. After the proclamation of martial rule in 1972, the aforesaid legal forces went underground, retained some of their activists aboveground and encouraged others to join the people's war in the countryside.
Mula maagang bahagi ng 1960, umunlad na ang ligal na kilusan ng mga patriyotiko at progresibong pwersa, na mas nauna sa digmang bayan na nagsimula noong 1969. Pagkaproklama ng batas militar noong 1972, kumilos na nang lihim ang mga nasabing ligal na pwersa, nagmantine ng ilang aktibistang ligal at naghikayat sa iba na lumahok sa digmang bayan sa kanayunan.