Siege of Angband
The Siege of Angband was the 400-year leaguer of the Noldor around the fortress of Morgoth in the early centuries of the First Age, which began following the Dagor Aglareb. The Noldor and their allies possessed insufficient force to assault Angband directly.
In the west Fingolfin and Fingon guarded the pass over Ered Wethrin into Hithlum from Barad Eithel, while Finrod and Orodreth held the pass of Sirion from Minas Tirith and Angrod with Aegnor held the northern slopes of Dorthonion to the borders of Aglon. In the east the Sons of Fëanor held watch; Celegorm and Curufin held the land between the rivers Aros and Celon, Maedhros had his stronghold on Himring while he guarded the Marches north of that hill and the plains between the rivers Celon and Gelion, Maglor kept watch over the northern hills of the river Gelion, and Caranthir in the shadows of Ered Luin.
It was during the Siege that Turgon's people left Nevrast to build Gondolin. Other Elven cities, Brithombar and Eglarest were also established by the Sindar on Falas, and Nargothrond, the realm of Finrod. The siege was incomplete, as Morgoth was still capable of sending out various forces of orcs to harass the elves, such as the attack of Hithlum; but the Noldor were grown strong enough, that these task forces posed no significant threat.
After about four hundred years, the Siege was broken in the Dagor Bragollach.