Going back in time, the next set of three hypotheses involves the fall of Constantinople on 29 May 1453. The first hypothesis is the one that I was taught at high school, in which a conjunction of the Moon and Venus was seen on the night before the city fell, and so was adopted as a good omen by the Turks under the Sultan Mehmet II. Another tradition is that the crescent commemorates the triumphal entry of the Sultan into the city under the crescent Moon. The third explanation involves a lunar eclipse on the evening of 22 May and a prophecy that the city could not be conquered while the Moon was waxing. The prophecy had greatly buoyed up the spirit of the Byzantines during the heavy attacks in the weeks before the eclipse. But when the lunar eclipse occurred, it emphasized that the Moon was waning, so the city was no longer protected by prophecy. The symbolism of a crescent arises from the shape of he visible Moon near the time of the umbral contact, when only a thin crescent of light remains.