Great Eulhae War

fusen loses some war and undergoes civil war during mid-late 1910s; slowly rebuilds but then great depression occurs; undergoes rapid military expansion after far-right Renewalists take power

This is the Sinju War. At the same time, Akitsukuni in the east is invading all of its neighbours to build a huge Akitsukunese/Fusenese Homeland that will stretch from Sinju to the eastern tip of Uju, which naturally also means they've been invading people's colonies and such. Following the victory in Fusen, the Allies then go and invade Akitsukuni to deal with this colony-stealing fucker who is later revealed to also be exterminating local populations. This is the Uju War.

Etymology
The Eulhae War started in 1935, with the year being 乙亥 (Eulhae) in the sexagenarian calendar cycle; this gave the name to the war. Actual hostilities started two months before the Eulhae year began, but it was only in the Eulhae year itself that the war truly became a global conflict. Historians at one time did not count the events that led to the actual fighting as part of the Eulhae War, but over time the name has become more symbolic than practical, and now represents the entire conflict from December 1934 to January 1941. 1935-02-04 (CNY 1935)

Uju
So the war begins with expansion into the light grey land possibly in 1933 or 34, but the world doesn't care because "the world" is mainly Sinju and Akitsukuni is the only nation in the area not made up of filthy natives. In 1935, unrelated to the Sinju War, Akitsukuni carries out a Pearl Harbour-style attack against the Meisaani Navy somewhere to slow the movement of reinforcements, then launch the massive Banzai zerg rush attack that only a Japan/Russia combo like Aki can pull off through the small country and across Tenzan into Elwha. They would also invade Sisimut at this time. I don't know how successful you will allow me to be in Elwha but ideally we push it to the breaking point and may even conquer it half-fully like France. However, by this time the Allies have defeated Fusen and march across Uju to face Akitsukuni, also launching a D-Day invasion of Elwha, possibly, and eventually pushing back into Akitsukuni. However, shortly after the death winter hits and along with poor public sentiment, stretched supply lines and fanatic enemies, when Akitsukuni proposes a conditional surrender in 1941 the Allies accept. They get to control some stuff which I haven't thought of yet, but the entire city of Tokyo is one and there will be a Heian Concession too