Flag of Vatican
|Design||A vertical bicolour of gold and white; charged with the Vatican City coat of arms centred. |
Starting in 1831, the papal infantry flew square yellow and white flags. At first they were diagonally divided, but after 1849 they were vertically divided like the merchant flag. The last infantry colour, adopted in 1862, was a plain square white and yellow flag.
On 8 February 1849, while Pope Pius IX was in exile in Gaeta, a Roman Republic was declared. The new government's flag was the Italian tricolor with the motto "Dio e Popolo" on the central stripe. The papal government and its flags were restored on 2 July 1849. On 20 September 1870 the Papal States were conquered by Italy and the yellow and white flags fell out of official use.
After the Lateran Treaty was signed in 1929, papal authorities decided to use the 1825 merchant flag as the state flag of the soon to be independent Vatican City state. However, the official drawing in the constitution used a drawing of the square 1862 infantry flag as a template. The treaty came into effect on 7 June 1929, and with it the newly-square Vatican flag. 
The Vatican City coat of arms is present in the white half. The coat of arms consists of: the papal tiara (as used under the pontificate of Pius XI), the two keys which represent the Keys of Heaven (according to the Gospel of Matthew 16:19) given by Jesus Christ to St. Peter, and a red cord connecting the keys. The popes are regarded as the successor of Peter, and the gold and silver keys have been significant elements in the symbolism of the Holy See since the 13th century. The gold represents spiritual power, while the silver key represents worldly power. The order of the keys on the coat of arms of Vatican City is the reverse of the coat of arms of the Holy See, in order to distinguish between the two entities.
The yellow and white of the flag also refer to the keys – in heraldic terminology, there is no distinction between yellow and gold (the metallic color or), nor between white and silver (argent). The Argent color has also been reported in relation with the white mountains of Lebanon and of the biblical city of Miye ou Miye according to the Lebanese Historian Anis Freiha.