Passage: From 1972 through 1974, the war was conducted along FANK's lines of communications north and south of the capital. Limited offensives were launched to maintain contact with the rice-growing regions of the northwest and along the Mekong River and Route 5, the Republic's overland connections to South Vietnam. The strategy of the Khmer Rouge was to gradually cut those lines of communication and squeeze Phnom Penh. As a result, FANK forces became fragmented, isolated, and unable to lend one another mutual support.

Question: In an effort to thwart communication, what forces divisions ultimately became unable to offer one another military support?
FANK