The Outer Dark

Leading up to the pending civil war that would spread across Union and much of corespace, leaders within the UN staffed at Yangra Station met with representatives from nearby systems. These meetings are known as the Assurance Summit.
During the Assurance Summit, negotiations were taking place between a multitude of political bodies. UN strategists, colonial leaders, corpro reps, community organizers, and many more all debated and argued over how to handle the coming conflict. Most importantly, they discussed how to prevent it from spreading to Midland.
In an effort to prevent Midland, a long-standing staple of corespace from falling victim to violent conflict, the Assurance Accords were signed by many (but not all) of midland's core and near-core worlds. These accords mandated the shutdown of Yangra Station's Blink Space Rectifier, effectively shutting down its Blink Gate and Omninet communication with the rest of Union, granted that half of the stationed UN fleet would return to Cradle to assist in the coming war.
As the final ship slipped back to Cradle, the gate closed behind them. And with it, so did Union. For decades, the sector operated autonomously under the newly formed Midland Defense Force, a coalition of UN and local peacekeeping troops. While a massive economic and material recession gripped the sector, it paled in comparison to the conflict that burned across much of Union corespace.
This period is referred to as the Outer Dark.
Eventually, contact was re-established with Union under their newly formed Third Committee. When UN ships arrived via nearlight travel, they saw Midland as a relic of a past time, remarkably preserved but still vulnerable to the drives and habits of SecComm rule. Eager to avoid any conflict political or otherwise, the UN commanders immediately conferred with the MDF to come to terms, allowing Midland to return to the galactic stage via blinkspace, while maintaining their relative autonomy.
An agreement was reached, after three years of fraught political struggle, and no way for the UN envoy to contact home during it, Midland's BSR was re-engaged, and Yangra Station's blink gate came back online for the first time in living memory. In exchange, the MDF remained as the sole responsible military body in the sector, granted it re-integrated with the command structure of the UN.
Today, the MDF is more a namesake of the UN inside if Midland, rather than a separate entity, and Midland once again enjoys a distal connection to Union corespace.