Konichiwa, here is the post about the Russo-Japanese War!
The Russo-Japanese War of 1903-1905
After the Chinese Civil War, Russia and Japan both had claims on Manchuria, with Japan wanting to hold it because of their colony of Korea and Russia wanting to maintain dominance their new port of Vladivostok in Outer Manchuria. The Japanese under Emperor Meiji established good relationships with the British, who wanted to limit Russia's power because of the threat to the British allies, most notably the Germans. Thus, Meiji declared war on the Russian Empire in July 1903, starting one of the most devistating wars up until that point.
The Japanese fleet, superior to the Russian navy in almost every regard, blockaded Port Arthur, a Russian-leased port in the small Chinese part of Inner Manchuria, and successfully sieged it, crippling the Russian's naval forces. The land battles were devistating, too, with Vladivostok falling to the Japanese on 9th January 1905.
This sucess of the Japanese was only possible because of the California Revolution, which resulted in California ceding away from Russia and becoming a new, independent nation. At first, the Russians tried to force the Californians back into their empire, but thanks to American support, the young republic was internationally recognized by December of 1904.
The war ended after the victory at the naval battle near Tsushima, where the Japanese fleet destroyed almost the entire Pacific Fleet. Shortly after that, the Treaty of Fort Ross was signed, in which Russia had to recognize California and cede Outer Manchuria to the Japanese and end their lease on Port Arthur. During the war more than 129,000 soldiers were killed, more than 34,000 men died from disease and 23,500 civilians died, resulting in a total of approximately 176,500 casualties, as well as approximately 152,000 wounded men.
One thing: California will never join the U.S. because of cultural differences, but they will be close allies.