Jeremiah prophesied against a nation that had broken their covenant with God. He foretells a time when God would replace that covenant with a new one. The New Covenant is based upon the shed blood of Christ.
As the Old Testament led up to Christ’s first coming, the New Testament has been leading up to this. Revelation 19 can be considered the climax of the entire Bible. The Messiah is coming, but no longer as a suffering servant. This time He comes as a conquering King, to judge evil and establish His kingdom on earth.