1. What is the background to Jesus’  revelation that satan is the serpent?
The truth that Jesus revealed that satan is the serpent was shown to me yesterday as I studied.  The truth is not overt, but rather hidden in the text of Luke 10 in which Apostle Luke wrote that Jesus sent out an additional seventy disciples to preach the gospel and to heal the sick in the cities of Israel.   The Apostle reported that the seventy returned with joy and reported to Jesus that EVEN the devils were subject (hypotassō/G 5293)   to them through His Name.
2. What did the disciples mean when they said that EVEN the devils were subject (hypotassō/G 5293) to them?
Devils had been harassing the Jewish population for centuries. The disciples were shocked when they discovered that demons of infirmity  fled at their presence and were cast out.   The usage of the word subject (hypotassō/G 5293) in related texts show that it carries the general meaning of OBEY, SUBDUE, SUBMIT.
Here are examples of texts in which the Greek word  hypotassō/G 5293  (subject) is used. When cross referenced back to Luke 10: 17, we see that:
  • the devils “Submitted themselves” 5293   (Romans 10: 3; 1 Corinthians 16: 16; Ephesians 5: 21 & 22)
  • the devils “are commanded to be under obedience”5293  (1 Corinthians 14: 34)
  • the devils are under their feet, a figurative expression referring to the posture of the conquered – 1 Corinthians 15: 27; Ephesians 1: 22.
  • the believers “subdued” the devils – 1 Corinthians 15: 28; Philomen 3: 21.
Now that my eyes are opened to this truth, I see clearly that Jesus gave a rather unexpected and indirect response to the disciples’ report that “even the devils are subject unto us!”    Lord Jesus responded that the root of the believer’s power is  SATAN’S EXPULSION FROM HEAVEN.    This is what He said –  “I beheld Satan as lightning fall from heaven” (Luke 10: 17).
Jesus chuckled in glee at the memory! Try to picture satan the insurgent being thrown out of heaven with such force that his fall looked like lightning!  This is a rather amusing incident from heaven’s point of view.   Apostle John explained that his expulsion was preceded by WAR:
And there was war in heaven: Michael and his angels fought against the dragon1404;; and the dragon1404; fought and his angels
And prevailed not; neither was their place found any more in heaven.
And the great dragon 1404 was cast out, that serpent3789, called the Devil 1228, and 2532 Satan 4567, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.
And I heard a loud voice saying in heaven, Now is come salvation, and strength, and the kingdom of our God, and the power of his Christ: for the accuser of our brethren is cast down, which accused them before our God day and night  (Revelation 12: 7– 10).
The background to the war was written in two PARABLES by Prophet Isaiah (chapter 14) and Prophet Ezekiel (chapter 28). In his parable, Prophet Ezekiel symbolically referred to satan as the Prince of Tyrus and the anointed cherub who was in Eden. Meantime, Prophet Isaiah referred to him as  the King of Babylon who had fallen from heaven.
4. Jesus used ASSOCIATION TO show the connection between Satan and his hosts as “serpents,”  “scorpions” and “the enemy” 
Lord Jesus continued to explain to the seventy that SATAN’S EXPULSION FROM HEAVEN is the reason why all believers are given “power to tread on serpent3789 and scorpions…and over all the power of the enemy” (Luke 10: 19).  
When we examine the text of Luke 10: 19,  we see that JESUS USED ASSOCIATION TO SHOW THAT SATAN IS THE SERPENT.  He did so by linking satan and his hosts with “serpents,”  “scorpions” and “the enemy”   Association is “a mental connection of ideas” (collinsdictionary.com).

And he said unto them, I beheld Satan as lightning fall from heaven.
Behold, I give unto you power to tread on  serpents3789 and scorpions 4651, and over all the power of the enemy 2190: and nothing shall by any means hurt you
Notwithstanding in this rejoice not, that the spirits are subject5293 unto you; but rather rejoice, because your names are written in heaven – Luke 10: 18 – 20.

Note that Apostles Paul and John used the same Greek word   Ophis/G3789 to refer to satan the serpent.  Read more in the post Satan The Serpent In The Fall Of Man And In Scripture”

More to come on   satan the serpent. Blessings, peace, angelic prosperity and protection.