The following verse and its mention of the well known numeric symbol 666 is one of the most iconic of those in the unique symbolic prophecy and narrative known as the Book of Revelation and St. John's Apocalypse, or just the Apocalypse.
All of them also conquered the area of ancient Israel and Judea, hence the relevance to the Hebrew prophecies. Starting with the Babylonian Empire, which was then conquered by the Persian Empire, which later fell to the Greek Empire via Alexander the Great's conquests, which subsequently fell victim to the Roman Empire. In Daniel it also makes a point to symbolize these four empires as the building blocks and components of one eventual final empire. Thereby, the Roman empire is the culmination of a process of each of the previous empires being gobbled up by the next, lending itself to the symbolism of beasts.