The Siege of Angband or "The Long Peace" in J. R. R. Tolkien's Middle-earth fictional universe was the siege of the Noldor around the fortress of Morgoth in the early centuries of the Years of the Sun, which began following the Dagor Aglareb. For the most part, it was a time of plenitude, peace and happiness for Elves and Men. The Long Peace lasted hundreds of years, during which time Men arrived over the Blue Mountains and the skill and prowess of the Noldor reached its peak.
The siege was incomplete, as Morgoth was still capable of sending out forces through secret passages from the towers of Thangorodrim to harass the Elves and to spy out Beleriand.
In one of these attacks, the first dragon, Glaurung, attacked. Immediately, the greater part of the Elven forces were driven back, and Lake Helevorn was defiled. However, the dragon was not yet fully grown, and his armour was still vulnerable. Fingon, leading a force of horse-borne archers, was able to drive the dragon back to Angband, winning great praise.
Afterwards, the Noldor grew strong, and sorties from Angband posed no significant threat. However, the Noldor and their allies possessed insufficient force to assault Angband directly. After nearly four hundred years, the siege was broken and the age of peace ended in the Dagor Bragollach (Battle of Sudden Flame); an onslaught of fire and ash Morgoth issued from Thangorodrim, providing cover for his advancing forces.