Following the expansion of the Iksandi Empire to the Iksandi Sea in the 900s A.D, a period of increased fishing and sailing occurred on the northern coast of the Iksandi sea. This drove a migration of sirens out of the northern parts of the sea into the southern region, pushing the population of sirens already living there farther southward.
It began in the 950s with a series of individual skirmishes among sirens. Northern sirens tend to solve conflicts individually, leading them to be surprisingly peaceful in small conflicts. However, the continued tension put a strain on both local populations and among the new migrants, many of whom were looking for a way to avoid the new Iksandi ships. In 962, the first major conflict of the war broke out when a group of sirens from the south attacked a traveling band of migrants who had overstayed their welcome, setting the precedent for eight years of hostility between the two groups.
Most of the conflicts were small and quickly resolved, comprising of raiding parties and fights over specific resources. Some of the bloodiest conflicts occurred at environmental boundaries, such as near shores and continental shelves. Both groups of sirens used these to their advantage, driving rivals into shallow ground where there is less chance of escape, or driving them to where the water is deeper and predators, such as sharks and sea drakes, lurk. Throughout the civil war, the Iksandi empire sought to claim the coastal sea as well, making it more difficult for sirens who wanted to return to their northern shores.
When the Iksandi Empire caught wind of the civil war through the records of sailors on the Iksandi sea, they sought to take advantage of the tension and lay claim to the waters for their own gain. They unleashed their own ships, most notably Kingsail, the first of its siren-hunting kind. The ship was lower to the sea than other ships and had a long keel to disrupt the waters and divide groups of sirens. Iksandi soldiers harpooned sirens from the ships, often capturing groups in nets and displaying them as spoils of war at carnivals and during festivals. The two groups of sirens formed a truce, seeing as both of their sides were equally hurt by the empire.
The civil war officially ended in 970, following several small truces and agreements between groups of sirens. Many sirens fled the Iksandi sea as the empire became fiercer and more determined to claim the sea, and the remainder fled to the deep, occasionally surfacing to attack Iksandi vessels or meet with the Merrows of the Azohican coast. By 1000, nearly all sirens in the Iksandi sea had disappeared or merged with the Merrows of the coast.