The Yuktobanian Revolution and establishment of the Union of Yuktobanian Socialist Republics troubled Emmerian monarchists and Verusan republicans, both of which feared similar uprisings in their working classes. The new Republic of Verusa, established two decades prior, after deposing a hapless imperial government that was subject to the whims of the West, also had ambitions to restore its control over the Usean Ocean, particularly Indus, Vedia, and other outlying, oil-rich islands to aid in its industrialization and promotion of national pride. Its military buildup began with the acquisition of Ugellan battleships to bolster its navy in 1930, and over the next decade strengthened its indigenous military industry along with Emmeria. Emmeria also spent this time expanding its colonial holdings in Europa and Sotoa, building up its petroleum reserves with Sotoan oil.
The war broke out in 1938, when Emmeria launched carpet bombing strikes against Yuktobanian industrial centers concurrent with an invasion along the northern coast. Verusa annexed the Yuktobanian Republics of Bulava and Molniya and launched a fleet from Tongbin towards Vedia. It arrived two weeks later, and both Indus and Vedia fell with little resistance. North Point was drained of resourced by the Usean War and declined to defend its colonies, withdrawing all Royal Navy forces to the home islands without a fight. Emmeria became bogged down in Borei as it attempted to push towards Cinigrad, and launched a secondary invasion force to the Pobeda peninsula, which approached Okchabursk by early 1940.
Bannion class battleships in the Pacific
Osean involvement in the war began after Verusa occupied the Comona Islands in 1940. After two years of negotiations intended to secure the archipelago for Verusa, Osea continued to request exclusive trade agreements such as those made between Usean and Anean powers and the old imperial regime in exchange for the islands. Frustrated and insulted by these demands, Verusa eventually resorted to invading Comona in September of 1940, destroying Osean Navy garrisons with surprise airstrikes before its invasion force landed. Osea's declaration of war against Verusa was followed by Emmeria declaring war against the Oseans, and Osea formally recognized the Yuktobanian communist regime for the first time in response.
While Osea's Atlantic Fleet was relatively strong when Verusa initiated hostilities, the result of a buildup during the Usean War, it was farther away from combat zones than the Pacific Fleet, which arrived at the Pobeda Peninsula to cut off Emmerian supply lines. The introduction of a competent naval force to their side greatly aided the Yuktobanians, who had neglected their maritime forces in favor of geostrategy since the Tsarist era. Osea did not land forces in the Atlantic Theater in 1940, however, only fighting the Emmerian Navy and deploying carrierborne fighters rather than braving a Yuktobanian winter.
Emmerian casualties in Okchabursk
Osean Marines landed at Comona in February of 1941 after setting up command infrastructure in Perfanesia, and initially suffered heavy losses due to unfamiliarity with jungle warfare. Indigenous insurgents aided the landing forces, but the Verusans' own guerrilla tactics proved highly effective against the more conventional Marine force. An Osean naval blockade managed to starve the occupiers of materiel, however, despite Verusa's attempts to break it. Following the sinking of the battleships Feng and Huang by the OFS Bannion in December 1941, Verusa's only Mizuho class battleships, the majority of the Verusan fighters surrendered.
The fighting in Yuktobania intensified despite Osea's attempts to blockade Pobeda, and Emmerian forces from the northern landing forces linked up with their eastern counterparts in July of 1941 in Okchabursk, opening up safer supply lines for the beleaguered invaders. However, even with both armies attacking Okchabursk, the city's defenders held their ground and inflicted great losses on the Emmerians while preventing them from marching on Cinigrad. The Emmerians' situation worsened in winter, when a Yutkobanian counteroffensive struck during a period of particularly bad weather. With assistance from Osean saturation bombing strikes, the Emmerians were drawn to the west of the city and attacked from two sides by the city's defenders and the incoming Yuktobanian reinforcements from Cinigrad. Less than ten percent of the Emmerian forces present managed to retreat north; those who routed in all other directions were killed by Yuktobanian forces.
Osean Marines in Indus
Osea devoted 1942 in the Usean Ocean to retaking Indus from Verusan occupation. The Marine Corps was retrained for jungle fighting based on experience in Comona and first landed in Indus in April 1942. Once again coordinated with local fighters, the liberation of Indus proceeded much more smoothly than Comona, especially with the destruction of much of Verusa's navy in 1941. An invasion of Vedia followed shortly afterwards, and the Usean Theater was largely resolved other than sporadic naval battles with Emmerian cruiser-destroyer groups operating out of Sotoa. The Oseans decided that they lacked sufficient assets in the Usean Ocean to invade Sotoa and instead used their naval dominance to supply Islamist rebels fighting the Emmerian occupation.
The Yuktobanian Army drove the Emmerians off of their continent in June of 1942 and launched attacks on Verusan forces in the South as well as beginning to build up an amphibious fleet for attacking the Anean mainland. Despite the civilian government's affinity for Yuktobania, Osean military planners feared the nation's potential for expansion and decided to take a more aggressive strategy to liberate occupied areas themselves so they would not be subject to Yuktobanian administration. Without informing the Yuktobanians, Osea launched a unilateral invasion of Emmeria in November of 1942, directly attacking Gracemeria due to the city's vulnerable position. Despite a large Emmerian naval presence in King's Bay, the supremacy of Osean airpower and battleship design proved decisive, and the Oseans managed to capture the royal family in the fighting. This was followed by Yuktobanian landings on the eastern and western shores of Anea, however, and both nations rapidly expanded their control over what remained of Emmeria.
The OFS Shelton shells Suzhou
Osea's role in the war with Verusa was eclipsed by its focus on controlling Emmeria, but continued to support the war effort with long-range airstrikes from the West Coast using newly-developed B-29 bombers. Verusa squandered many of its air assets in attempts to contain these strikes, culminating in Osea's victory at the Battle of Sand Island. Yuktobania had difficulty mustering a large offensive force, and while it did launch an expedition into Verusa, its subterfuge had a far greater strategic effect. The NKVD infiltrated Verusan cities, arming and consulting communist partisans. A major uprising in Jinsha led to the establishment of a communist government, forcing the Verusan army to devote forces away from the front and allowing Yuktobania to advance on Xueyu with little opposition. With Yuktobania closing on Shangdu several weeks later, the Nationalist government fled south, and communist revolutionaries established the People's Republic of Verusa, allied with Yuktobania, in the former Nationalist capital.
Dismayed by the unhindered growth of communism in the Eastern Hemisphere and after secretly demanding that Yuktobania reach a ceasefire with the Verusan nationalists for several months, in October of 1943 Osea allied itself with the Nationalist regime and deployed troops to its frontlines in the Longsheng Plains. Yuktobania and the Verusan communists declared war on Osea, and combat in Longsheng was coupled with limited hostilities in Anea. Although the Oseans held their ground in Verusa, Clavian rebels opposed to Verusan rule came to the communists' aid in return for promised independence. Ultimately the Nationalists withdrew to modern-day West Clavis and Yuktobanians were forced off of the Western front in Emmeria before Osea completed the development of nuclear weapons. Following a demonstration on Solo Island in the Ceres Ocean, Yuktobania and Verusa signed the Treaty of Okchabursk, ceasing hostilities and recognizing the sovereignty of the Democratic Republic of Clavis, Socialist Republic of Clavis, Republic of Emmeria, and Federal Socialist Republic of Estovakia.