Origins of Crescent and Star symbol

According to legend in 339 BC the city of Byzantium, (later known as Constantinople and then Istanbul), won a decisive battle under a brilliant waxing moon which they attributed to their patron Goddess Artemis (Diana in Roman mythology) whose symbol was the crescent moon In honor of Artemis the citizens adopted the crescent moon as their symbol (though some legends attribute the adoption to a Roman victory against the Goths on the first day of the lunar month). When the city became the Christian Roman Constantinople in 330 AD, Constantine also added the Virgin Mary's star on the flag. As such, it has been claimed that when the Ottoman Turks conquered Constantinople (Istanbul) in 1453, they adopted the city's existing flag and symbol.However, the most common theory in Turkey is that the crescent and star symbol was adopted by Ottoman Empire after a bloody war in Balkans. After seeing the reflection of crescent and star on to the blood of soldiers, Ottoman Sultan decided to adopt a new flag to honor the soldiers who died for the sake of their country.

http://en.wikipedia.org/wiki/Star_and_crescent