Complex sentence: Observing a lack of ground foliage he was concerned about the possibility of extensive Viet Cong defensive works close to the LZ, and with the support of Williamson it was subsequently switched to a less-exposed location.
Split into simpler sentences: Observing a lack of ground foliage he was concerned about the possibility of extensive Viet Cong defensive works close to the LZ. With the support of Williamson, the landing zone was subsequently switched to a less-exposed location.