Just before the famous Battle of the Milvian Bridge in 312, the emperor Constantine witnessed a sign in the sky, a cross with next to it written “In this sign, you shall conquer”. The vision appeared before his final fight with the rival emperor Maxentius. The vision left a deep impression on Constantine who then had the shields of his soldiers marked with the Christian monogram XP, representing the two letters chi (X) and rho (P) of the Greek alphabet, the first two letters of the Greek word Christos, meaning “anointed”, epithet attributed to Jesus. The next day he confronted the enemy army and defeated it. This marked the beginning of a new chapter in the Roman Empire and the victory of Christian faith over paganism. A year later, he issued the Edict of Milan (also known as the Edict of Constantine), which ended three centuries of oppression, persecution and martyrdom of Christians. 2012 marks 1700 years since this famous battle. Vatican City and Italy will commemorate it with a joint postal issue. The miniature sheet reproduces a painting by Giulio Romano in the Sala di Costantino of the Vatican Museums. The work is better known as “The battle against Maxentius at the Milvian Bridge”. Pope Leo X commissioned it in 1517 to Raphael who, busy with many other tasks, only began to work on it shortly before he died. Giulio Romano, a student of his school, finished the work.