Since when have JWs said that United Nations will launch an attack on religion? I was reading some publications at wol.jw.org about the Jehovah's Witnesses beliefs pertaining to the end of the world, such as this article from which I quote below snippet:


  5 What yet unseen event will take place next? Paul stated: “Whenever
  it is that they are saying: ‘Peace and security!’ then sudden
  destruction is to be instantly upon them.” The first phase of this
  “sudden destruction” is the attack against “Babylon the Great,” the
  world empire of false religion, also known as “the harlot.” (Rev.
  17:5, 6, 15) That attack against all forms of false religion,
  including Christendom, is the start of the “great tribulation.” (Matt.
  24:21; 2 Thess. 2:8) For many, this event will come as a surprise.
  Why? Because up to that point, the harlot will confidently view
  herself as “a queen” who will “never see mourning.” But she will
  suddenly discover that she has miscalculated her chances of survival.
  She will be wiped out rather quickly, as if “in one day.”—Rev. 18:7,
  8.
  
  6 God’s Word identifies the harlot’s attacker as a “wild beast” with
  “ten horns.” A study of the book of Revelation shows that the wild
  beast refers to the United Nations (UN). “The ten horns” represent all
  present political powers that support this “scarlet-colored wild
  beast.”* (Rev. 17:3, 5, 11, 12) How devastating will the attack be?
  The nations of the UN will plunder the harlot’s wealth, expose her
  real character, devour her, and “completely burn her.” Her destruction
  will be final.


What I wanted to know is, is this some modern idea among Jehovah's Witnesses that United Nations will attack religion? Or since when have they believed that this is what those events in the book of Revelation refer to?
Even before the United Nations existed, Jehovah's Witnesses have held the position that the United Nations is going to destroy false religion. The belief originates from back when its predecessor, the League of Nations, was formed in 1920.

Christian clergymen at that time were heralding the League of Nations as the organization that would bring about the Kingdom of God. This was seen as a big warning sign to the Bible Students at that time, since 1914 was believed to have been when Jesus began ruling over God's Kingdom from heaven, and the League of Nations was clearly being formed as mankind's attempt at world peace, not God's.

Here are some older Watchtower publications which describe these events:


w53 9/15 "Flight to Safety with the New World Society" para. 19, 20
g85 10/8 "A Vision Rejected"
w85 10/1 "A 'Disgusting Thing' Fails to Bring Peace" para. 12-14
w54 11/15 "Is World Unity a Dream?" para. 15