The War of Eastern Expansion, also known as the Eastern Conquest, was a joint invasion of the Triple Alliance by the Legacy of Delor and Sarken Hegemony. Over the course of five years and hundreds of battles in Triple Alliance space, the worlds of Hahio and Niata were taken from Triple Alliance control and expanded their control of the eastern Known Galaxy.
After the integration of the qualls of Telpker in 2958, the Sarken Hegemony had not significantly grown in nearly 400 years. Likewise, the Legacy of Delor had had minimal success in expanding to the southeast with their colonization efforts. With the Angel Sector to their west, the uncharted regions to the south and east, and the constant border skirmishes with the Jiptohr Empire, Bolaemia Bureaucracy, Triple Alliance inhibiting trade to the north, the growth of both nations had been slowed down considerably. Eventually, both nations began to discuss the potential economic benefits of annexing resource-rich worlds from one of their smaller neighbors.
The militarized Jiptohr and populous Bolaemia were less desireable targets than the Triple Alliance due to their considerable militaries, but the smaller Triple Alliance was a much more vulnerable target. However, the possibility of either nation coming to the aid of the Alliance was another factor to consider. In late 3219, though, with the Expansion War engulfing both the Empire and Bureaucracy in total war, it meant that neither nation could come to the aid of the Alliance without pulling resources from their current war and risking heavy losses.
In late 3320, Legacy and Hegemony forces launched a simultaneous assault of all Triple Alliance systems and instituted a blockade, while ground forces additional fleets moved in on the systems containing the planets Hahio and Niata. Over the course of several months, the allied powers worked extensively to secure their footholds in the two systems, took over local production, and reinforced the planets with fleet garrisons, orbital systems, and other defenses.
In 3325, nearly over five years of fighting, the conflict drew to a close with the Treaty of Hahio. In exchange for the formal recognition of Hahio and Niata as Legacy and Hegemony territories, open hostilities ceased and the invading forces withdrew from the rest of Triple Alliance space.