From the reading I've done on this, it seems pretty clear, as Little Hawk indicates, that the Alamo slaughter was needless.

General Houston, in charge of the regulars, had in fact sent Jim Bowie to carry the word to destroy the Alamo and retreat to a more defensible position--as originally a mission, it was not a good place to be besieged. But what appears to have happened in that when Bowie got there he was so impressed with what had been done to improve the position, and possibly convinced it was essential as a forward post, that he decided to stay and improve it further. (If it was only 5 feet off the ground. this is puzzling). Houston had sent a message to Governor Smith (governor of what I don't know, since Texas was neither a country not a state--he seems to have been the head of a governing committee a la the Continental Congresses). Houston told Smith the Alamo should be abandoned if Smith saw fit. Gov. Smith did not see fit.