Sources such as diaries though not very reliable can be used if there are a large amount of them showing the same date and event. Historical books written about the event especially those closer to the time would be able to help determine that the date is accurate as well.
1) There would be a gradual withdrawal of American troops from South Vietnam.
2) The South Vietnamese would take greater responsibility for the fighting.
<span>Kings at the time usually didn't have heirs to the throne, because of this by killing the king you bring confusion to the country. No one knows what to do and everyone wants to be the new leader. So the king dying was a great chance for Alexander to take over Persia.</span>