A bit of history
Of the earlier known prophetic texts of Israel, we find a variety of delivery styles: plain oration, song, poetry, etc. There is a fair amount of figurative speech, but the messages are more or less straightforward: God is coming to judge Judah! He will raise up Nebudchadnezzar against Tyre! He will deliver Moab to the Edomites!
But during and after the exilic period, we see some variation emerge with the prophet Ezekiel: his final chapters (c.585 and 572 BC) bring in some extensive symbols, and his vision of a new Jerusalem requires an angelic guide. In Zechariah 1-8 (c.520-518 BC), the writer has a series of highly symbolic visions, again requiring an angelic guide.
Israelite history is murky in the middle of the Second Temple era, but by the time we get to the beginning of the second century, we find that a new genre has emerged. The elements of prophetic delivery that were forming in Ezekiel and Zechariah (and may indeed have been influenced by the Babylonian and Persian cultures during that vague era of history) have been incorporated into a distinct style of literature: the Jewish apocalypse.
The apocalyptic genre
Not all apocalypses exhibit the exact same traits, but they are mostly consistent in their similarities:
- Dualism: there is demonic evil and there is divine good, and they are in combat. There will be an era of intense divine warfare, manifesting as conflict between God's chosen people and the wicked rulers of the world, but this era will be replaced by a future era of righteousness.
- Determinism: God is in control of history, so despite all the evil in the world, everything happens according to his will. He is in charge, and he is bringing history toward its goal.
- Judgment: there will be sudden intervention by God in the history of the world, bringing all evil to an end. All humanity, or at least the people alive at the time this happens, will be held accountable for their actions. The righteous will inherit the coming age, while the wicked will suffer punishment.
- Visions: the revelation of all this information comes in the shape of visions or dreams, filled with intense symbolism. Consequently, the seer himself often requires the help of an angel to explain the meaning of the symbols. (Hence why scholars have come to call this genre 'apocalypse'; this is a Greek word that describes the 'revealing' of this new information.)
- Pseudepigraphical: all apocalypses are attributed to an authoritative figure of the past, in order to lend credibility to the revelations described. Examples include: Enoch, Abraham, Moses, Baruch, Ezra, Daniel, etc. Later Christians would attribute their visions to: Peter, Paul, James, John, Thomas, etc.
- Sealing: because the apocalyptic revelations are always about events in the near future, even the very present, an author needs an explanation for why the book is only just now being published. It was, many apocalypses inform the reader, the seer received his visions centuries, even millennia ahead of time, and was told to seal the scroll and hide it; only when the time was right would the scroll be rediscovered (i.e. the time when the author wrote the book).
With all of the above drawn together, we see that the general thrust of the apocalyptic genre is that its subject matter is primarily concerned with a crisis in the author's present time. For Ezekiel and Zechariah, the crisis was the Babylonian exile. For the earlier swath of Jewish apocalypses, it was the Maccabean Revolt. For later apocalypses, it was the Roman conquest of Jerusalem and its aftermath; the Revelation was written in this latter time period, as were 4 Ezra and 2 Baruch).
The Revelation hits all of the major points of a Jewish apocalypse, except for two. First, while all other known Jewish apocalypses are pseudepigraphical, the general consensus of scholars and critics is that the Revelation is an extremely rare exception, perhaps the only exception: the seer is exactly who he claims to be (a Jewish-Christian named John, probably living in the late first-century AD). Second, because the Revelation is not pseudepigraphical, the author has no reason to allege that he was told to seal up his visions until some distant future date; instead, the author admits to living during the very time his visions are concerned with, and in the last chapter his angelic guide forbids him from sealing his scroll.
The symbolism of the Revelation
The Revelation exhibits exactly the sort of symbolism we would expect from any ancient Jewish apocalypse. So while the Revelation's symbols are intense and cryptic, this was common for the genre as a whole. In that case, we should be asking, 'Why does the apocalyptic genre use so much symbolism at all?'
In apocalyptic literature in general, many of the symbols are drawn from the Hebrew scriptures and broader Jewish and Christian traditions. When we come to the Revelation, this is the case with the absolute majority of the symbols. Revelation 5, for example, portrays the messiah (Jesus, in this case) as 'the lion of the tribe of Judah' who is the 'root of David'. Right around the same time as the Revelation, another Jewish apocalypse, 4 Ezra, was written. The author of this book, who was not a Christian, also symbolizes the Davidic messiah as a lion. In this case, the Revelation and 4 Ezra were both drawing on a by-then traditional combination of Genesis 49.9 and Jeremiah 23.5. The intention wasn't to hide the true meaning behind obscure pictures, but to show the intended recipients of the text something they would understand in an evocative manner.
But other symbols in the apocalypses were drawn from popular cross-cultural traditions and myths. For example, the sequence of four metals in Daniel 2 is found in many cultures even before the sixth century, including Greece and Persia. Or the general picture of a cloud-riding ruler triumphing over sea-monster(s) in Daniel 7 is loosely influenced by the ancient story of Baal slaying the sea-monster Yam. Although it was typical for apocalypses to use heavy symbolism, their (probable) meanings would have been easy to discover for anyone who knew the sources being used. The absolute majority of the symbols in the Revelation came from Jewish and Christian traditions, but what about some of those other symbols? Things like...
Imagine if someone living right now wrote a book with symbolism that said:
I saw an eagle with thirteen feathers, colored red and white and blue. Over time it grew thirty-five more feathers. Then many nations waged war on the eagle. But the eagle threw burning fire on its enemies two times, and the war ended. After this, I saw the eagle grow two more feathers. And then I saw...
One-thousand years, maybe two-thousand years from now people may not understand any of what this is supposed to be describing just by reading it at face value. They'd have to do some serious research to figure it out. But we know about a major country today that has these symbols on its money, on its flag, and in its history books. We have no problem recognizing the symbols and their meaning.
Let's suppose some sort of imperial authority got his hands on a copy of the Revelation; would he have been able to detect the anti-Roman message of the book? Even if the Jewish and Christian symbols fly over his head, he's not going to miss the message when he sees the book calling Roma, the personification of the city on seven hills, a 'whore'.
To the point:
Was the Revelation written in code to hide it from the Romans?
No. The Revelation is a Jewish apocalypse, a genre known for its heavy use of symbolism. Most of the symbols came from common Jewish and Christian sources, but the symbols that are most aggressively anti-Roman are the symbols that would be most obvious to the Romans themselves.
John J. Collins. The Apocalyptic Imagination: An Introduction to Jewish Apocalyptic Literature.
Craig C. Hill. In God's Time: The Bible and the Future. (My list of apocalyptic traits was adapted from Hill's, found in chapter four.)