Empress Gao
The relationship between Emperor Xiaowu and Gao soon deteriorated, as Emperor Xiaowu, wanting to assert his authority, grew increasingly distant from Gao and tried to befriend the independent generals Yuwen Tai, who controlled the western provinces of the empire, and Heba Sheng (賀拔勝), who controlled the southern provinces, to counter Gao. In 534, believing Emperor Xiaowu to be on the cusp of taking coordinated action with Yuwen and Heba, Gao marched on the capital Luoyang to try to reassert control over the imperial government. Emperor Xiaowu, believing himself to be unable to withstand a Gao attack, fled to Yuwen's domain. Empress Gao did not follow him, but no formal divorce was ever proclaimed by either side, and Emperor Xiaowu did not create another empress. Gao subsequently declared Emperor Xiaowu's distant nephew Yuan Shanjian the Heir Apparent of Qinghe emperor (as Emperor Xiaojing), creating the split between Eastern Wei (with Emperor Xiaojing as its emperor) and Western Wei. Around the new year 535, Yuwen, whose own relationship with Emperor Xiaowu had deteriorated after he refused to condone Emperor Xiaowu's incestuous relationships with his cousins and had killed Yuan Mingyue (元明月) the Princess Pingyuan, who was having a relationship with Emperor Xiaowu, poisoned Emperor Xiaowu to death. When news of Emperor Xiaowu's death reached Eastern Wei, a debate occurred as to whether he should be officially mourned, and the turning issue of the debate toward the eventual decision to mourn him was the fact that no divorce was ever declared between him and Empress Gao.