Not sure if you are reading the articles right or just isolating paragraphs from multiple watchtowers. The JW's see two fulfillments in all prophecies from Isaiah and this teaching has at least remained consistent since 1954.
First Fulfillment:
The nation was Israel (physical Israel) was born in the Sinai wilderness and was crushed in 607 when Babylonians destroyed Jerusalem. In fulfillment of Isaiah 66:8, the nation was reborn in 537 BCE when King Cyrus released the Jews and the worship in Jerusalem began.
Larger fulfillment:
In the modern day, the new nation (spiritual Israel) was born in 33 CE during the outpouring of the Holy Spirit, when the Jews were rejected and the Christian congregation became the new spiritual Israel. However, it was overpowered by the "weeds" of Christendom and was reborn in 1919 when the anointed was released from Babylonian captivity.