The history of the glorious flag of the Republic of Genoa goes back to very old times; according to some historians, it was a reward from the crusades for the help given by the genoese troops and fleet in the conquest of Jerusalem during the First Crusade.

Many other great countries in the world adopt the St. George's Flag as their national flag. One of them is England. There a very interesting story about the relationship between the genoese flag and the english one:

It is believed to have been adopted for the uniform of English soldiers during the Crusades of the eleventh, twelfth and thirteenth centuries.^[84] From about 1277 it became the national flag of England. St George's Cross was originally the flag of Genoa and was adopted by England and the City of London in 1190 for their ships entering the Mediterranean to benefit from the protection of the powerful Genoese fleet. The maritime Republic of Genoa was rising and going to become, together with its rival Venice, one of the most important powers in the world. The English Monarch paid an annual tribute to the Doge of Genoa for this privilege. The cross of St George would become the official Flag of England.

A red cross acted as a symbol for many Crusaders in the twelfth and thirteenth centuries. It became associated with St George and England, along with other countries and cities (such as Georgia, Milan and the Republic of Genoa), which claimed him as their patron saint and used his cross as a banner. It remained in national use until 1707, when the Union Flag (also known as the Union Jack, especially at sea) which English and Scottish ships had used at sea since 1606, was adopted for all purposes to unite the whole of Great Britain under a common flag. The flag of England no longer has much of an official role, but it is widely flown by Church of England properties and at sporting events.

(font: Wikipedia)