Actually, the Society does not claim that the Bible Students were on a parity with other religious groups in 1918 when Jehovah is said to have "judged" Babylon the Great. They were already in the line of "witnesses of Jehovah" supposedly in existence for millennia, made up with anointed 144,000 at the time. Thus, they were already sounding the warning about 1914 in advance unlike all other Christians. (I'm stating their official position, mind you) If you read the Revelation Climax book, you will see that the Society claims that the Bible Students were already the "two witnesses" (= the John class) of Revelation 11:3-4 who "prophesied" for 1,260 days from October 1914 to Spring 1918.
What the Society claims happened in 1918 is that Jehovah came into his spiritual "Temple" (which they interpret to be God's organization) accompanied with the new king Jesus whose task was to cleanse it, removing the people that Jehovah judges to be unfit. This doctrine, like all others having to do with 1918 and 1919, originated with Rutherford and was most fully developed in the 1933 book Preparation. This is an interpretation of Malachi 3:1-3 which claims that God and the "messenger of the covenant" will come to the Temple, who "must sit as a refiner and cleanser of silver and must cleanse the sons of Levi, and he must clarify them like gold and like silver, and they will certainly become to Jehovah people presenting a gift offering in righteousness" (NW). Of course, I have never understood how Jehovah was not present in his Temple or organization all along, and dating the fulfillment of this to 1918 is pure assertion. The reason why they use this date is that the Finished Mystery book (published in 1917) prophesied falsely that the "fall of Babylon" was going to happen in April 1918, "with church members killed by the millions". Rutherford rescued this false prophecy by claiming that the fall did happen but invisibly (just as the second coming really happened in 1874 but was invisible), and he appealed to Malachi 3:1-3 as proof that this "fall from grace" did happen and occurred when Jehovah tested and refined his people. Hence, the circular reasoning that Jehovah came into his Temple in 1918.
There was another motivation for asserting that 1918 was year that Babylon fell and "Jehovah came into his Temple". It just so happened to provide a beautiful explanation for all the momentous events that happened to the Bible Students in 1918 and 1919. Instead of Christendom being judged and destroyed in April 1918 as the Finished Mystery prophesied, something entirely unexpected happened: the Society itself started behaving in a very "un-Christian" way (according to the standards of Bible Students then and JWs now) by publishing patriotic pro-U.S. statements, appeals to purchase Liberty Bonds, and a direction for Bible Students to join the rest of Christendom in a national day of prayer for an Allied victory in the War. This compromise was of course due to the fact that the government was putting pressure on the Society on account of their encouragement of pacifist insubordination in Army boot camps, and the arrests and trial of Society officers soon followed. Then they were put in prison, and meanwhile there was a lessening off of the preaching work by Bible Students (tho not a complete cessation as the Society exaggerates)....not because of persecution per se but because the Finished Mystery claimed that the harvest would end in 1918. Then unexpectedly the Society officers were released from prison in 1919 and Rutherford asserted that a whole new preaching work (i.e. the Elisha work) was now supposed to begin for the preparation of the Kingdom.
By claiming that Babylon did fall spiritually in 1918, Rutherford was able to explain why the Society behaved the way it did....it temporarily became part of Babylon the Great. Today the Society talks about Jehovah's Witnesses coming under "spiritual captivity to Babylon" in 1918, likening "spiritual Israel" to literal Israel's captivity to Nebuchadnezzar's kingdom. Rutherford also interpreted the "two witnesses" of Revelation 11 as also figurative of this experience; God allowed Satan's forces to "slay" his prophets (dated exactly to April 1918 from the 1,260 days mentioned in Revelation), temporarily bringing an end to their activity, before raising them up again in 1919. The experience of trial and imprisonment would also correspond to the "testing" and "refining" of Malachi 3:1-3. The Society today also uses this metaphor of testing to explain why so many Bible Students left the Watchtower Society at this time...they were the chaff cast out of God's organization. Then, when the organization was finally refined, God began to protect it from Satan's forces -- allowing it to begin life anew as a "new nation". This idea was advanced in Rutherford's controversial "Birth of a Nation" article from 1925, which -- in an interpretation of Revelation 12 -- claimed that a heavenly war occurred in 1914 and Satan's forces were cast to the earth, where they began to persecute the organization (= the woman) in 1918. The rescue of the woman from the Dragon to a place in the wilderness for 1,260 days (Revelation 12:6) was then interpreted as the favor and divine protection that God provides his people from 1919 to 1922. It was during this period that Rutherford mobilized his people into a well-organized preaching campaign (the "Millions" campaign). Rutherford claimed that 1,260 days from March 27, 1919 (the day the work was restored after the release of Rutherford and his men from prison) led exactly to September 8, 1922 which was the day that Rutherford gave his "Advertise, Advertise, Advertise" talk. Rutherford claimed that God then allowed Satan to attack his people from 1922 onward, not because he no longer supported them but because he was using them to vindicate his name and prove Satan a liar, i.e. that they would stand firm like faithful Job.
One problem is why there was a delay between 1914 and 1918. If Satan and his demons were thrown to the earth in that year and if consecrated from the 144,000 were already on earth at that time, why did Satan wait until 1918 (or the Fall of 1917, appealing to the Hebrew calendar) to persecute God's people? Rutherford explained: "After this battle, he [Satan] must have been so dazed for some time that he did not realize what had happened to him ... it required some time to wake up to the fact" (Watchtower, 1 March 1925, p. 70). Rutherford was serious about this...he did not intend this as a joke.
As you can see, all of this was incredibly convoluted and rested on ad hoc interpretations of various scriptures (like Malachi 3 and Revelation 11-12) that had nothing really to do with each other. Rutherford however was a better writer than Franz would later be, and was able to package all of this in a much easier-to-understand and common-sense way than is apparent from Watchtower publications from the 1950s onward.
