The 7th century was a time of upheaval. In the west, the Goths, Franks, and Lombards were building a new, medieval world upon the ruins of the Western Roman Empire, while in the east, the remnant of the once mighty empire was fighting for its very survival. The constant war against the Persians had irreparably eroded the eastern parts of the kingdom. Powerlessly, the Romans witnessed the fall of Jerusalem in 614 and Alexandria in 619. The empire was also under siege from the northern Avar and Slavic tribes who invaded via the Danube, plundering and vandalizing as they moved closer and closer to the capital until they ultimately stood in front of the city gates of Constantinople in 626.