against international law to sail without showing the flag of the nation owning the ship. Sailing without a flag is not uncommon for pirates or slavers. Any naval vessel would challenge any ship sailing without a flag.
it was likely this incident that triggered Beauregard’s attack on Sumter.”
Beauregard already had orders from Davis to reduce the fort by force prior to Lane’s incident with Nashville. He opened fire after Anderson refused his last offer to surrender.
Clearly neither Pirates or Slavers would be going up the channel at Charleston Harbor.
More like, the ship regarded itself as Confederate, but didn't want to provoke a bad reaction from a clearly Union vessel, and so chose not to run up a flag or show lights in the hopes they would be ignored. When it was fired upon, it ran up the Stars and Stripes, again, probably to avoid further entanglement with this apparently hostile ship.
Beauregard already had orders from Davis to reduce the fort by force prior to Lane’s incident with Nashville.
From the Secretary of War Walker, and those orders gave Beauregard whatever leeway he needed to make the decision, and they even went so far as to allow a peaceful conclusion.
I believe those orders of which you speak were days old at the time.
He opened fire after Anderson refused his last offer to surrender.
Not quite the whole story. He opened fire after Anderson refused his offer of a truce if Beauregard's forces had to defend themselves from the coming Union warships.
I've seen the messages. Beauregard said he would not fire on Anderson if Anderson agreed to not fire on him, should the ships engage Beauregard's forces. Anderson replied that if Beauregard's forces fired on any of those ships, Anderson would fire on him with the guns of Sumter.
Anderson, together with Lincoln sending those ships, left Beauregard with no acceptable alternative choice.