Complex sentence: This move was seen as a way to placate national, Congressional and international concerns, to progress arms-control talks and to stymie the outcry over the use of non-lethal chemical agents in Vietnam.
Split into simpler sentences: This move was seen as a way to placate national, Congressional, and international concerns. It was also seen as a way to progress arms-control talks, additionally it could have stymied the outcry over the use of non-lethal chemical agents in Vietnam.