Complex sentence: By the end of November, the North Vietnamese withdrew back into their sanctuaries in Cambodia and Laos, having failied to wipe out a major American unit, yet forcing the U.S. Army to pay a high price.
Split into simpler sentences: By the end of November, the North Vietnamese withdrew back into their sanctuaries in Cambodia and Laos. Failing to wipe out a major American unit, yet the PAVN had forced the U.S. Army to pay a high price.