In the Siege of Jerusalem of 614, after 21 days of relentless siege warfare, Jerusalem was captured. Byzantine chronicles relate that the Sassanids and Jews slaughtered tens of thousands of Christians in the city, many at the Mamilla Pool, and destroyed their monuments and churches, including the Church of the Holy Sepulchre. This episode has been the subject of much debate between historians. The conquered city would remain in Sassanid hands for some fifteen years until the Byzantine emperor Heraclius reconquered it in 629.