Complex sentence: North Korean troops in the Rocky Crags, which extended from Sobuk-san toward P'il-bong, took cover during air strikes, and napalm, bombs, and strafing had little effect.
Split into simpler sentences: North Korean troops in the Rocky Crags, which extended from Sobuk-san toward P'il-bong, took cover during air strikes. Napalm, bombs, and strafing had little effect.