The prophecy where these symbols are found begins with Revelation 12. The dragon who tried to destroy Christ at His birth is Satan (Revelation 12:9), who stirred up Herod to put the Savior to death. But the Roman Empire was the agent Satan used to make war on Christ and His people during the first centuries, and paganism was its prevailing religion. So in a secondary sense, the dragon is a symbol of pagan Rome. LF 181.2
Revelation 13 presents another beast, “like a leopard,” to which the dragon gave “his power, his throne, and great authority.” This symbol, as historically most Protestants have believed, represents the papacy, which took over the power and seat and authority that the Roman Empire once held. The Bible says about this leopardlike beast: “He was given a mouth speaking great things and blasphemies.... Then he opened his mouth in blasphemy against God, to blaspheme His name, His tabernacle, and those who dwell in heaven. It was granted to him to make war with the saints and to overcome them. And authority was given him over every tribe, tongue, and nation” (Revelation 13:2, 5-7). This prophecy, nearly identical with the description of the little horn of Daniel 7, unquestionably points to the papacy. LF 181.3
“He was given authority to continue for forty-two months”—the three years and a half, or 1,260 days, of Daniel 7—during which the papal power was to oppress God's people. This period, as stated in earlier chapters, began with the supremacy of the papacy, A.D. 538, and ended in 1798. At that time the papal power received its “deadly wound,” and the prediction was fulfilled, “He who leads into captivity shall go into captivity.” LF 181.4