[Formendacil]

In many respects this is an unanswerable question. If you have The Silmarillion, you already "know" about as much as anyone else does about what happened in Middle-earth between the sack of the Havens and the end of the War of Wrath.

And this isn't just an uncertain ground because Tolkien never revisited this part of the Silmarillion after he finished The Lord of the Rings--which is case with the Tale of the Nauglamír--it's a part of the story that he never really addressed at all, except in the outline-esque early 1920s "Qenta Noldorinwa." Aside from that, the only references to what happened in Middle-earth during those years are only to be found in scattered notes and outlines (such as the Tale of the Years mentioned by Galin).

Basically, the final chapter of the "Quenta Silmarillion" section of The Silmarillion contains as good a reconstruction of what happened as any--with added bonus that it was put together by his son and editor.