There was no assault on Ft. Moultrie, at least until it was abandoned by Anderson, whereupon the South Carolinians did seize it (and since it wasn't actually their property, it really WAS a seizure). But Anderson's orders didn't tell him that he had to wait for an all-out assault. His orders of December 11 told him that he need only "have tangible evidence of a design to proceed to a hostile act" and that he had in abundance. Pickens threat to put state troops into Sumter, the armed patrol boats who, when asked what they were doing, responded "you'll find out in a week" warnings that civic leaders would try to control the mob, but that the forts would be theirs "one way or another" (Klein, 152), and provided Anderson with plenty of evidence of design.
Very good.
"His orders of December 11 told him that he need only "have tangible evidence of a design to proceed to a hostile act"
So, where was the tangible evidence?