How can iron be "one solid piece" once it is mingled with clay? So you might want to give that some further thought and then make the necessary adjustments in your thinking.
The Roman Empire passed away a long time ago.
That is when the statue divided into 10 toes.
But the countries which were within it remain to this day, and they certainly DO NOT have the strength or the ascendancy which Rome had. That is what the iron represented,
Rome is the city harlot that sits on the 7 heads of the beast, she exists at the time of the 7 heads, and after the 7th head, and on into the 8th head. She does not end and start again.
After the Roman Empire fell, the RCC took the place of Caesar and Caesar worship, an image of the Roman Empire, and took over the persecution of Israel until 1967.
Do you say that the iron ended at the fall of the Roman Empire? The statue doesn't show that, the iron continues after that event.
Show me in the statue, where the Roman Empire falls.
and it does not exist any more.
The statue shows the gentile nations that rule over Israel until they are restored to Jerusalem. Since 1967 the statue has ended.
This does not mean that the nations cease to exist, only that they do not dominate Israel anymore.
And it is out of that group of nations that the Antichrist will make his appear.
Rev 17:11, The beast of 7 heads is the 8th head, and one of the seven.
How is he the 8th head, if the beast with 7 heads is Rome?
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The Antichrist, the 8th head, is one of the 7 heads , he is Caesar. But the 8th head rules from the death of the 7th head until perdition.
So he rules Israel from the fall of the Roman Empire until Israel is restored to Jerusalem.