You are right and you bring up a good question. What would have happened if the ships never made it to Charleston on time or Beauregard withheld forcing Fort Sumter to evacuate; leaving forcing Lincoln to act first by reenforceing Fort Pickens against the truce. This would have led to a standoff where Fort Sumter's forces would have had to leave on their own in disgrace, and the Federal Government breaking their word by using force at Fort Pickens. The call for troops by Lincoln would have taken a different political light or even may have been politically impossible to do.

David