By 1830, the United Provinces of Mornaea had expanded from the Pacific coast to the borders of the Green Confederacy, governed by a unique political system defined by the "Charter" and the "Lee Compromise," which balanced power between an elected Emperor and a popular Diet. However, this delicate balance collapsed following the contentious 1834 election of Emperor Jiang Weiguo. Unpopular with both the aristocracy and the commoners, Weiguo found himself paralyzed by a hostile Diet that exploited constitutional loopholes to block his legislation and tax levies. This political dysfunction culminated in 1836 during a diplomatic crisis with the native Green Confederacy; when the Emperor attempted to bypass the legislature to fund frontier defenses, the Diet retaliated by completely defunding the military, plunging the republic into a constitutional crisis just as war broke out.

The resulting conflict, known as the "Eastern Struggle," initially proved disastrous for the under-supplied Mornaean forces. At the Battle of Green Plain in 1839, a Mornaean militia was overrun by the Aarde and Ruiter armies simply because they ran out of ammunition, forcing a humiliating retreat. The specter of total defeat compelled the political factions in Pingcheng to compromise in 1840; the Diet restored military funding in exchange for constitutional reforms. With its supply lines restored, the professional Mornaean army crushed the Green Confederacy by 1845, reducing the native nations to client states. To prevent future paralysis, the government ratified the "Lang Plan," creating a Senate to mediate disputes and formally admitting the frontier territories of Zandvlakte and Shuang-Ho as provinces.

Simultaneously, the republic underwent rapid industrialization, striving to become the "World's Loom" to rival Britain's textile dominance. Hampered by a lack of domestic coal on the island of Hoshih, the French entrepreneur Jean-Baptiste Fournier founded a railway company in 1838 to bridge the gap to the resource-rich Snowy Mountains. Despite the immense difficulty of constructing a line through the "Green Hell"—a refugium filled with aggressive fauna and hostile natives—the railway was completed in 1850. The resulting influx of coal supercharged the Mornaean economy, leading to a surge of Asian immigration that unsettled the traditional aristocracy, who viewed the newcomers as a threat to the republic's character.

In the eastern half of the continent, the independent Anglo and Dutch states faced economic ruin due to British intervention. In the 1840s, Britain launched a crusade against the Atlantic slave trade, seizing ships and blockading the cotton exports of the southern "Zud" states. While the industrial northern states remained solvent, the plantation-based economies of the south collapsed under the debt and the loss of their primary export market. Exploiting this desperation, the United Provinces offered to pay off the states' debts and negotiate with Britain in exchange for annexation. Despite deep cultural reservations regarding Han rule and the UPM's different approach to slavery, the threat of financial cataclysm forced the European states to capitulate. On January 1, 1853, following the signing of the "Eternal Agreement of Communion," the Anglo and Dutch republics were absorbed into the United Provinces, transforming the nation into a multi-ethnic empire spanning the entire continent.