Now that we’ve had the direct storytelling thrust of the Darkening of Valinor, Tolkien takes a step back to when Melkor was chained for three ages. Lúthien is born at the end of this first age. The Dwarves awaken during the second. The great halls of Khazad-dûm are crafted, as are the Caves of Menegroth, the home to King Thingol and Queen Melian of the Sindarin people. And the first meeting of Elves and Dwarves. While the Dwarves were eager to learn what the Elves had to offer, they kept their own ways to themselves. This was partly due to cultural pride, and partly because the Elves thought everything about the Dwarves and their culture was less beautiful, and therefore less worthy.
The frustrating note here is that there is much that happens off camera, such as the awakening of the Dwarves. That’s understandable when we consider that The Silmarillion is the history according to the Elves. If they didn’t see it, we only get any hearsay they chose to document.
Under Thingol and Melian, the Sindar prospered in wisdom and skill to be recognized as the pinnacle of their race in Arda. Ultimately, as we know, Melkor kills the Two Trees with the aid of Ungoliant, and after being rebranded as Morgoth, he returns to Angband and strengthens his dominion of fell creatures. Melian’s power keeps Ungoliant from entering Menegroth, but it could not shield the Elves from random Orc attacks throughout the wood and across the lands. The dark armies went forth and assailed King Thingol, who in turn called upon Denethor and other allies, fighting the first battle in the Wars of Beleriand. Victory came at a heavy price as the war claimed Denethor. Thingol was cut off and came too late, and he did avenge Denethor, though the Elves of Ossirland never took another king, and they never again went to open war.
The attack upon Cirdan was successful, with Thingol’s people being driven to the edge of the sea. Gathering as many into the realm as possible at Doriath, Melian created a magic fence of sorts, the Girdle of Melian, to keep a Morgoth’s servants at bay. Outside the fence, the dark armies roamed free, ever the threat.