Of course, this is just my opinion. Since the Watchtower has many ridiculous teachings, it is actually difficult to boil it down to just one, but in my opinion, this is the worse.
*** REVELATION CLIMAX chap. 26 p. 172 pars. 4-5 God's Sacred Secret, Its Glorious Climax! ***4 When the sounding of the seven trumpets got under way in 1922, the Bible Students' convention at Cedar Point, Ohio, featured a talk by the president of the Watch Tower Society, J.F. Rutherford, based on the scripture "The kingdom of heaven is at hand." (Matthew 4:17, King James Version) He concluded with these words: "Then back to the field, O ye sons of the most high God! Gird on your armor! Be sober, be vigilant, be active, be brave. Be faithful and true witnesses for the Lord. Go forward in the fight until every vestige of Babylon lies desolate. Herald the message far and wide. The world must know that Jehovah is God and that Jesus Christ is King of kings and Lord of lords. This is the day of all days. Behold, the King reigns! You are his publicity agents. Therefore advertise, advertise, advertise, the King and his kingdom." God's Kingdom by Christ Jesus was brought to the fore, and that set off the great surge of Kingdom preaching that has included the judgments heralded by the sounding of all seven of the angelic trumpets.5 The trumpet blast of the seventh angel was reflected in highlights of the Bible Students' convention in Detroit, Michigan, July 30-August 6, 1928.
1. 1922 Cedar Point, Ohio: A challenge to Christendom's leaders in religion, politics, and big business to justify their failure to bring peace, prosperity, and happiness. Messiah's Kingdom is the panacea.
2. 1923 Los Angeles, California: The public talk, "All Nations Now Marching to Armageddon, but Millions Now Living Will Never Die," called on peace-loving "sheep" to abandon the death-dealing sea of humanity. (hyh)
3. 1924 Columbus, Ohio: Ecclesiastics indicted for self-exaltation and refusal to preach Messiah's Kingdom. True Christians must preach God's vengeance and comfort mourning humanity.
4. 1925 Indianapolis, Indiana: A message of hope contrasting the spiritual darkness in Christendom with the bright Kingdom promise of peace, prosperity, health, life, liberty, and eternal happiness.
5. 1926 London, England: A locustlike plaguing of Christendom and its clergy, exposing their rejection of God's Kingdom, and hailing the birth of that heavenly government.
6. 1927 Toronto, Canada: An invitation, carried as by armies of cavalry, calling on people to forsake 'organized Christianity' and give heart allegiance to Jehovah God and to his King and Kingdom.
7. 1928 Detroit, Michigan: A declaration against Satan and for Jehovah, making plain that God's anointed King, enthroned in 1914, will destroy Satan's evil organization and emancipate mankind.
Looks like trumpet #2 was off key!
Some of the "trumpet blasts" refer to things that they have since changed even before the Revelation book was printed. I seem to remember something about the elder arrangement being one of the "blasts" but has since been changed.
It is sickening the Watchtower teach this stuff about the 7 trumpets to this day. They are very keen in linking dates of conventions with scripture. Rutherford started all that. It is absurd that the date of a convention was foretold in the bible. That is sheer lunacy. The core of Watchtower doctrines are based on the dates of conventions. This alone convicts the Watchtower of being a false prophet of the highest degree.