As Constantine Porphyrogennetos' warnings show, the ingredients and the processes of manufacture and deployment of Greek fire were carefully guarded military secrets. So strict was the secrecy that the composition of Greek fire was lost forever and remains a source of speculation. Consequently, the "mystery" of the formula has long dominated the research into Greek fire. Despite this almost exclusive focus, however, Greek fire is best understood as a complete weapon system of many components, all of which were needed to operate together to render it effective. This comprised not only the formula of its composition, but also the specialized dromon ships that carried it into battle, the device used to prepare the substance by heating and pressurizing it, the "siphōn" projecting it, and the special training of the "siphōnarioi" who used it. Knowledge of the whole system was highly compartmentalised, with operators and technicians aware of the secrets of only one component, ensuring that no enemy could gain knowledge of it in its entirety. This accounts for the fact that when the Bulgarians took Mesembria and Debeltos in 814, they captured 36 "siphōns" and even quantities of the substance itself, but were unable to make any use of them.